Merge pull request #22135 from Rostepher/fix-overlay-builds-5.0

[Build System: CMake] Correctly set the Darwin deployment targets when building the overlay projects (5.0 branch).

Author: najacque

cmake/modules/StandaloneOverlay.cmake

@@ -60,7 +60,7 @@ precondition(TOOLCHAIN_DIR)
 
 # Some overlays include the runtime's headers,
 # and some of those headers are generated at build time.
-add_subdirectory("${SWIFT_SOURCE_DIR}/include" "swift/include")
+add_subdirectory("${SWIFT_SOURCE_DIR}/include" "${SWIFT_SOURCE_DIR}/include")
 
 # Without this line, installing components is broken. This needs refactoring.
 swift_configure_components()