build: compatibility for CMake 3.4.3
build: compatibility for CMake 3.4.3

CMake 3.4.3 does not support the copy files... <directory> pattern.  Add
compatibility for it.

e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation