Driver: extract modules flag handling (NFC)
Driver: extract modules flag handling (NFC)

Extract a function to render the options related to modules.  This
reduces the cyclomatic complexity of the `ConstructJob` function.  NFC.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@312330 91177308-0d34-0410-b5e6-96231b3b80d8

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