clang: Support providing lld linker in toolchain

Add new TOOLCHAIN_CONFIG flag that enables the lld project in the
built toolchain.

6 files changed, 160 insertions, 17 deletions

diff --git a/README.md b/README.md
index 9a33264..5124a71 100644
--- a/README.md
+++ b/README.md
@@ -195,6 +195,8 @@ Fields for building the toolchains:
   `clang-tidy`. Additionally, Clang versions `18` and newer will also include
   the *external project*
   [Include What You Use](https://github.com/include-what-you-use/include-what-you-use).
+- `INCLUDE_LLD`:
+  For `clang` toolchains, add the LLD linker to toolchain. (default: `false`)
 
 Fields for using the toolchains
 (within [Justbuild](https://github.com/just-buildsystem/justbuild) projects):
diff --git a/src/compilers/clang-16-native.TARGETS b/src/compilers/clang-16-native.TARGETS
index e19e4de..0cf9e65 100644
--- a/src/compilers/clang-16-native.TARGETS
+++ b/src/compilers/clang-16-native.TARGETS
@@ -170,6 +170,18 @@
                           }
                         , "then": ["clang-tools-extra"]
                         }
+                      , { "type": "if"
+                        , "cond":
+                          { "type": "lookup"
+                          , "key": "INCLUDE_LLD"
+                          , "map":
+                            { "type": "var"
+                            , "name": "TOOLCHAIN_CONFIG"
+                            , "default": {"type": "empty_map"}
+                            }
+                          }
+                        , "then": ["lld"]
+                        }
                       ]
                     }
                   }
diff --git a/src/compilers/clang-17-native.TARGETS b/src/compilers/clang-17-native.TARGETS
index 78b2bd4..3f0837f 100644
--- a/src/compilers/clang-17-native.TARGETS
+++ b/src/compilers/clang-17-native.TARGETS
@@ -170,6 +170,18 @@
                           }
                         , "then": ["clang-tools-extra"]
                         }
+                      , { "type": "if"
+                        , "cond":
+                          { "type": "lookup"
+                          , "key": "INCLUDE_LLD"
+                          , "map":
+                            { "type": "var"
+                            , "name": "TOOLCHAIN_CONFIG"
+                            , "default": {"type": "empty_map"}
+                            }
+                          }
+                        , "then": ["lld"]
+                        }
                       ]
                     }
                   }
diff --git a/src/compilers/clang-18-native.TARGETS b/src/compilers/clang-18-native.TARGETS
index 3a75343..4860702 100644
--- a/src/compilers/clang-18-native.TARGETS
+++ b/src/compilers/clang-18-native.TARGETS
@@ -65,10 +65,7 @@
   { "type": ["@", "rules", "CC/foreign/shell", "data"]
   , "arguments_config": ["TOOLCHAIN_CONFIG"]
   , "project": ["patched_sources"]
-  , "localbase":
-    [ "binutils_dir"
-    , ["@", "iwyu", "", "sources"]
-    ]
+  , "localbase": ["binutils_dir", ["@", "iwyu", "", "sources"]]
   , "cmds":
     [ { "type": "join"
       , "$1":
@@ -154,6 +151,48 @@
         , "-DLLVM_INCLUDE_DOCS=OFF"
         , "-DLLVM_INCLUDE_TESTS=OFF"
         , "-DLLVM_INSTALL_TOOLCHAIN_ONLY=ON"
+        , { "type": "join"
+          , "$1":
+            [ "-DLLVM_ENABLE_PROJECTS="
+            , { "type": "join_cmd"
+              , "$1":
+                [ { "type": "join"
+                  , "separator": ";"
+                  , "$1":
+                    { "type": "++"
+                    , "$1":
+                      [ ["clang"]
+                      , { "type": "if"
+                        , "cond":
+                          { "type": "lookup"
+                          , "key": "INCLUDE_LINTER"
+                          , "map":
+                            { "type": "var"
+                            , "name": "TOOLCHAIN_CONFIG"
+                            , "default": {"type": "empty_map"}
+                            }
+                          }
+                        , "then": ["clang-tools-extra"]
+                        }
+                      , { "type": "if"
+                        , "cond":
+                          { "type": "lookup"
+                          , "key": "INCLUDE_LLD"
+                          , "map":
+                            { "type": "var"
+                            , "name": "TOOLCHAIN_CONFIG"
+                            , "default": {"type": "empty_map"}
+                            }
+                          }
+                        , "then": ["lld"]
+                        }
+                      ]
+                    }
+                  }
+                ]
+              }
+            ]
+          }
         , { "type": "if"
           , "cond":
             { "type": "lookup"
@@ -168,12 +207,11 @@
             { "type": "join"
             , "separator": " "
             , "$1":
-              [ "-DLLVM_ENABLE_PROJECTS='clang;clang-tools-extra'"
-              , "-DLLVM_EXTERNAL_PROJECTS=iwyu"
+              [ "-DLLVM_EXTERNAL_PROJECTS=iwyu"
               , "-DLLVM_EXTERNAL_IWYU_SOURCE_DIR=${LOCALBASE}/iwyu"
               ]
             }
-          , "else": "-DLLVM_ENABLE_PROJECTS=clang"
+          , "else": ""
           }
         , "-DLLVM_ENABLE_RUNTIMES='libcxx;libcxxabi;libunwind'"
         , "-DLLVM_TARGETS_TO_BUILD=X86"
diff --git a/src/compilers/clang-19-native.TARGETS b/src/compilers/clang-19-native.TARGETS
index 6ab96c3..652d329 100644
--- a/src/compilers/clang-19-native.TARGETS
+++ b/src/compilers/clang-19-native.TARGETS
@@ -65,10 +65,7 @@
   { "type": ["@", "rules", "CC/foreign/shell", "data"]
   , "arguments_config": ["TOOLCHAIN_CONFIG"]
   , "project": ["patched_sources"]
-  , "localbase":
-    [ "binutils_dir"
-    , ["@", "iwyu", "", "sources"]
-    ]
+  , "localbase": ["binutils_dir", ["@", "iwyu", "", "sources"]]
   , "cmds":
     [ { "type": "join"
       , "$1":
@@ -154,6 +151,48 @@
         , "-DLLVM_INCLUDE_DOCS=OFF"
         , "-DLLVM_INCLUDE_TESTS=OFF"
         , "-DLLVM_INSTALL_TOOLCHAIN_ONLY=ON"
+        , { "type": "join"
+          , "$1":
+            [ "-DLLVM_ENABLE_PROJECTS="
+            , { "type": "join_cmd"
+              , "$1":
+                [ { "type": "join"
+                  , "separator": ";"
+                  , "$1":
+                    { "type": "++"
+                    , "$1":
+                      [ ["clang"]
+                      , { "type": "if"
+                        , "cond":
+                          { "type": "lookup"
+                          , "key": "INCLUDE_LINTER"
+                          , "map":
+                            { "type": "var"
+                            , "name": "TOOLCHAIN_CONFIG"
+                            , "default": {"type": "empty_map"}
+                            }
+                          }
+                        , "then": ["clang-tools-extra"]
+                        }
+                      , { "type": "if"
+                        , "cond":
+                          { "type": "lookup"
+                          , "key": "INCLUDE_LLD"
+                          , "map":
+                            { "type": "var"
+                            , "name": "TOOLCHAIN_CONFIG"
+                            , "default": {"type": "empty_map"}
+                            }
+                          }
+                        , "then": ["lld"]
+                        }
+                      ]
+                    }
+                  }
+                ]
+              }
+            ]
+          }
         , { "type": "if"
           , "cond":
             { "type": "lookup"
@@ -168,12 +207,11 @@
             { "type": "join"
             , "separator": " "
             , "$1":
-              [ "-DLLVM_ENABLE_PROJECTS='clang;clang-tools-extra'"
-              , "-DLLVM_EXTERNAL_PROJECTS=iwyu"
+              [ "-DLLVM_EXTERNAL_PROJECTS=iwyu"
               , "-DLLVM_EXTERNAL_IWYU_SOURCE_DIR=${LOCALBASE}/iwyu"
               ]
             }
-          , "else": "-DLLVM_ENABLE_PROJECTS=clang"
+          , "else": ""
           }
         , "-DLLVM_ENABLE_RUNTIMES='libcxx;libcxxabi;libunwind'"
         , "-DLLVM_TARGETS_TO_BUILD=X86"
diff --git a/src/compilers/clang-20-native.TARGETS b/src/compilers/clang-20-native.TARGETS
index 047f7c8..f7c6c3c 100644
--- a/src/compilers/clang-20-native.TARGETS
+++ b/src/compilers/clang-20-native.TARGETS
@@ -151,6 +151,48 @@
         , "-DLLVM_INCLUDE_DOCS=OFF"
         , "-DLLVM_INCLUDE_TESTS=OFF"
         , "-DLLVM_INSTALL_TOOLCHAIN_ONLY=ON"
+        , { "type": "join"
+          , "$1":
+            [ "-DLLVM_ENABLE_PROJECTS="
+            , { "type": "join_cmd"
+              , "$1":
+                [ { "type": "join"
+                  , "separator": ";"
+                  , "$1":
+                    { "type": "++"
+                    , "$1":
+                      [ ["clang"]
+                      , { "type": "if"
+                        , "cond":
+                          { "type": "lookup"
+                          , "key": "INCLUDE_LINTER"
+                          , "map":
+                            { "type": "var"
+                            , "name": "TOOLCHAIN_CONFIG"
+                            , "default": {"type": "empty_map"}
+                            }
+                          }
+                        , "then": ["clang-tools-extra"]
+                        }
+                      , { "type": "if"
+                        , "cond":
+                          { "type": "lookup"
+                          , "key": "INCLUDE_LLD"
+                          , "map":
+                            { "type": "var"
+                            , "name": "TOOLCHAIN_CONFIG"
+                            , "default": {"type": "empty_map"}
+                            }
+                          }
+                        , "then": ["lld"]
+                        }
+                      ]
+                    }
+                  }
+                ]
+              }
+            ]
+          }
         , { "type": "if"
           , "cond":
             { "type": "lookup"
@@ -165,12 +207,11 @@
             { "type": "join"
             , "separator": " "
             , "$1":
-              [ "-DLLVM_ENABLE_PROJECTS='clang;clang-tools-extra'"
-              , "-DLLVM_EXTERNAL_PROJECTS=iwyu"
+              [ "-DLLVM_EXTERNAL_PROJECTS=iwyu"
               , "-DLLVM_EXTERNAL_IWYU_SOURCE_DIR=${LOCALBASE}/iwyu"
               ]
             }
-          , "else": "-DLLVM_ENABLE_PROJECTS=clang"
+          , "else": ""
           }
         , "-DLLVM_ENABLE_RUNTIMES='libcxx;libcxxabi;libunwind'"
         , "-DLLVM_TARGETS_TO_BUILD=X86"