cmake: specify stdlib and overlays with an API library-level

Author: nkcsgexi

stdlib/cmake/modules/SwiftSource.cmake

@@ -476,6 +476,7 @@ function(_compile_swift_files
   # The standard library and overlays are built resiliently when SWIFT_STDLIB_STABLE_ABI=On.
   if(SWIFTFILE_IS_STDLIB AND SWIFT_STDLIB_STABLE_ABI)
     list(APPEND swift_flags "-enable-library-evolution")
+    list(APPEND swift_flags "-Xfrontend" "-library-level"  "-Xfrontend" "api")
   endif()
 
   if(SWIFT_STDLIB_SINGLE_THREADED_RUNTIME)