[driver] -mkernel implies -fno-builtin, so claim the arg to avoid an unused argument warning. Part of rdar://11120518
[driver] -mkernel implies -fno-builtin, so claim the arg to avoid an unused
argument warning.
Part of rdar://11120518


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@153469 91177308-0d34-0410-b5e6-96231b3b80d8

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