Restrict test to macOS

Author: edymtt

validation-test/BuildSystem/dsymutil_jobs.test

@@ -2,7 +2,7 @@
 # RUN: mkdir -p %t
 # RUN: SKIP_XCODE_VERSION_CHECK=1 SWIFT_BUILD_ROOT=%t %swift_src_root/utils/build-script --dry-run --darwin-install-extract-symbols --dsymutil-jobs 5 --cmake %cmake 2>&1 | %FileCheck %s
 
-# REQUIRES: standalone_build
+# REQUIRES: standalone_build,OS=macosx
 
 # CHECK: --- Extracting symbols ---
 # CHECK: { "command": "dsymutil", "start": "