Enable CI for macOS targets

Author: phausler

.github/workflows/pull_request.yml

@@ -11,6 +11,7 @@ jobs:
     with:
       linux_exclude_swift_versions: "[{\"swift_version\": \"5.9\"}, {\"swift_version\": \"5.10\"}]]"
       windows_exclude_swift_versions: "[{\"swift_version\": \"5.9\"}]"
+      enable_macos_checks: true
       enable_wasm_sdk_build: true
       wasm_sdk_build_command: swift build -Xcc -D_WASI_EMULATED_PTHREAD