Merge pull request swiftlang#37793 from gottesmm/pr-241389d143d39eb74eeb012c95ed83257a90c198

[cmake] Disable swift-cmake tests on non-Darwin platforms.

Author: gottesmm

validation-test/BuildSystem/CMakeLists.txt

@@ -1,5 +1,7 @@
 
-# Only test this if we found a Swift compiler.
-if (CMAKE_Swift_COMPILER)
+# Only test this if we found a Swift compiler. Currently only enable this test
+# if we build on Darwin since we do not have a host toolchain available when
+# compiling on the bots for Linux meaning this path would not be tested.
+if (CMAKE_Swift_COMPILER AND APPLE)
   add_subdirectory(swift-cmake)
 endif()