Driver: extract debugging related options (NFC)
Driver: extract debugging related options (NFC)

Out-of-line the logic for selecting the debug information handling.
This is still split across the new function and partially inline in the
job construction.  This is needed since the split portion attempts to
record the "-cc1" arguments.  This needs to be the very last item to
ensure that all the flags are recorded.  NFC.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@312435 91177308-0d34-0410-b5e6-96231b3b80d8

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