Fix Linux libc++ usage. Somehow this slipped through during the port.
Fix Linux libc++ usage. Somehow this slipped through during the port.

Test cases for this and all the rest of the port are still in the works,
but will wait for a fixed computer and post 3.0 merging...

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@143916 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang