[Testing] Unbreak unified build testing

This test assumes an Apple platform but for reasons unknown, the Linux
bots (wrongly?) consider this test to be unsupported.

(cherry picked from commit ab2f6c7)

Author: davezarzycki

validation-test/Reflection/reflect_Optional_Any.swift

@@ -8,6 +8,7 @@
 
 // REQUIRES: reflection_test_support
 // REQUIRES: executable_test
+// REQUIRES: OS=macosx || OS=tvos || OS=watchos || OS=ios
 // UNSUPPORTED: use_os_stdlib
 
 import SwiftReflectionTest