clang-cl: Alias /Zi and /Z7 to -gline-tables-only
clang-cl: Alias /Zi and /Z7 to -gline-tables-only

LLVM only knows how to emit Z7-style line tables on -win32, so there's
no reason for clang to emit anything other than line info.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@201017 91177308-0d34-0410-b5e6-96231b3b80d8

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