[clang] add requirements to -Wa,-W test cases.
[clang] add requirements to -Wa,-W test cases.

Include linux as a test requirement.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@374837 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang