[Driver][XRay][test] Update the macOS support check

For macOS, the code says, the XRay flag is only supported on x86_64.
Updating the test and making that check explicit.

Differential Revision: https://reviews.llvm.org/D85773

clang/test/Driver/XRay/xray-instrument-os.c

@@ -1,4 +1,4 @@
 // RUN: not %clang -o /dev/null -v -fxray-instrument -c %s
-// XFAIL: -linux-, -freebsd, -darwin, -macos
+// XFAIL: -linux-, -freebsd, x86_64-apple-darwin, x86_64-apple-macos
 // REQUIRES: amd64 || x86_64 || x86_64h || arm || aarch64 || arm64
 typedef int a;