[5.7-04182022] Tidy up build flags and fix implicit import circular dependency (#392)#408

rxwei wants to merge 1 commit intoswiftlang:swift/release/5.7-04182022swiftlang/swift-experimental-string-processing:swift/release/5.7-04182022from

rxwei:cherry-392-5.7-04182022rxwei/swift-experimental-string-processing:cherry-392-5.7-04182022Copy head branch name to clipboard