Use the '-define-availability' frontend flag directly in CMake rules (#529)

Author: stmontgomery

cmake/modules/shared/AvailabilityDefinitions.cmake

@@ -7,14 +7,10 @@
 # See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 
 # Settings which define commonly-used OS availability macros.
-#
-# These leverage a pseudo-experimental feature in the Swift compiler for
-# setting availability definitions, which was added in
-# [apple/swift#65218](https://github.com/apple/swift/pull/65218).
 add_compile_options(
-  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend \"AvailabilityMacro=_mangledTypeNameAPI:macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0\">"
-  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend \"AvailabilityMacro=_backtraceAsyncAPI:macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0\">"
-  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend \"AvailabilityMacro=_clockAPI:macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0\">"
-  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend \"AvailabilityMacro=_regexAPI:macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0\">"
-  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend \"AvailabilityMacro=_swiftVersionAPI:macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0\">"
-  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend \"AvailabilityMacro=_distantFuture:macOS 99.0, iOS 99.0, watchOS 99.0, tvOS 99.0, visionOS 99.0\">")
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -define-availability -Xfrontend \"_mangledTypeNameAPI:macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0\">"
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -define-availability -Xfrontend \"_backtraceAsyncAPI:macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0\">"
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -define-availability -Xfrontend \"_clockAPI:macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0\">"
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -define-availability -Xfrontend \"_regexAPI:macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0\">"
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -define-availability -Xfrontend \"_swiftVersionAPI:macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0\">"
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -define-availability -Xfrontend \"_distantFuture:macOS 99.0, iOS 99.0, watchOS 99.0, tvOS 99.0, visionOS 99.0\">")