imports: Switch to Microsoft GSL implementation

... with two minor code base changes compared to previous
use of gsl-lite:

- dag.hpp: ActionNode::Ptr and ArtifactNode::Ptr are not
  wrapped in gsl::not_null<> anymore, due to lack of support
  for wrapping std::unique_ptr<>. More specifically, the
  move constructor is missing, rendering it impossible to
  use std::vector<>::emplace_back().

- utils/cpp/gsl.hpp: New header file added to implement the
  macros ExpectsAudit() and EnsureAudit(), asserts running
  only in debug builds, which were available in gsl-lite but
  are missing in MS GSL.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/buildtool/multithreading/task_system.cpp b/src/buildtool/multithreading/task_system.cpp
index cf9ed543..13c3caec 100644
--- a/src/buildtool/multithreading/task_system.cpp
+++ b/src/buildtool/multithreading/task_system.cpp
@@ -14,7 +14,7 @@
 
 #include "src/buildtool/multithreading/task_system.hpp"
 
-#include "gsl-lite/gsl-lite.hpp"
+#include "gsl/gsl"
 #include "src/buildtool/multithreading/task.hpp"
 
 TaskSystem::TaskSystem() : TaskSystem(std::thread::hardware_concurrency()) {}
@@ -59,7 +59,7 @@ void TaskSystem::Finish() noexcept {
 }
 
 void TaskSystem::Run(std::size_t idx) {
-    gsl_Expects(thread_count_ > 0);
+    Expects(thread_count_ > 0);
 
     while (not shutdown_) {
         std::optional<Task> t{};