[MachineOutliner] NFC - simplify -moutline/-mno-outline logic
[MachineOutliner] NFC - simplify -moutline/-mno-outline logic

It's a bit cleaner to use `hasFlag` instead of nested ifs. This
just refactors the -moutline/-mno-outline logic to use that.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@335549 91177308-0d34-0410-b5e6-96231b3b80d8

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