[NinjaBuildCommand] Factor out helper for checking if we can update-if-newer.
[NinjaBuildCommand] Factor out helper for checking if we can update-if-newer.
apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild