Swift: disallow WIN32_EXECUTABLE properties

Currently, the compiler does not synthesize the correct entry point for
the application and passing the subsystem flag does not work the same
way with the Swift linker language.  Add a check to prevent the
application of `WIN32_EXECUTABLE` to Swift executables until they can be
properly supported.  This will prevent the need for a future policy
change.

Closes: #19325

1 files changed, 1 insertions, 0 deletions

diff --git a/Source/cmGlobalGenerator.h b/Source/cmGlobalGenerator.h
index dcd8c5f..db96489 100644
--- a/Source/cmGlobalGenerator.h
+++ b/Source/cmGlobalGenerator.h
@@ -609,6 +609,7 @@ private:
   virtual void ForceLinkerLanguages();
 
   bool CheckTargetsForMissingSources() const;
+  bool CheckTargetsForType() const;
 
   void CreateLocalGenerators();