Merge pull request #71989 from apple/empty-abi-stdlib

cmake: avoiding generating ABI baseline files when building stdlib

Author: nkcsgexi

stdlib/cmake/modules/SwiftSource.cmake

@@ -583,6 +583,11 @@ function(_compile_swift_files
     list(APPEND swift_flags "-swift-version" "5")
   endif()
 
+  # Avoiding emiting ABI descriptor files while building stdlib.
+  if (SWIFTFILE_IS_STDLIB)
+    list(APPEND swift_flags "-Xfrontend" "-empty-abi-descriptor")
+  endif()
+
   if(SWIFTFILE_IS_SDK_OVERLAY)
     list(APPEND swift_flags "-autolink-force-load")
   endif()