[driver] Ignore the '--' option, rather then fail. Do so to match gcc's  behavior. rdar://10110352 and PR10908
[driver] Ignore the '--' option, rather then fail. Do so to match gcc's 
behavior.
rdar://10110352 and PR10908

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@139551 91177308-0d34-0410-b5e6-96231b3b80d8

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