[5.9][Explicit Modules] Have `-clang-target` on Darwin platforms set to the SDK version by-default#1322

artemcm merged 1 commit intoswiftlang:release/5.9swiftlang/swift-driver:release/5.9from

artemcm:59ClangTargetAtSDKTripleartemcm/swift-driver:59ClangTargetAtSDKTripleCopy head branch name to clipboard