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, 1 insertions, 1 deletions

diff --git a/etc/dev/TARGETS b/etc/dev/TARGETS
index 40fdcf52..725f884e 100644
--- a/etc/dev/TARGETS
+++ b/etc/dev/TARGETS
@@ -11,7 +11,7 @@
   , "targets":
     [ ["@", "ssl", "", "crypto"]
     , ["@", "grpc", "", "grpc++"]
-    , ["@", "gsl-lite", "", "gsl-lite"]
+    , ["@", "gsl", "", "gsl"]
     , ["@", "fmt", "", "fmt"]
     , ["@", "cli11", "", "cli11"]
     , ["@", "json", "", "json"]