test: macOS on ASi conforms to the stable ABI

Configure the test suite properly for the expected ABI for macOS on ASi.

Author: compnerd

test/lit.cfg

@@ -708,6 +708,10 @@ if (run_os == 'maccatalyst'):
   target_os_abi = 'macosx'
   target_os_is_maccatalyst = "TRUE"
   config.available_features.add("OS=ios")
+# macOS on ASi uses the stable ABI
+if run_os in ('macosx',) and run_cpu in ('arm64',):
+  target_mandates_stable_abi = "TRUE"
+  config.available_features.add('swift_only_stable_abi')
 if (run_os in ['linux-gnu', 'linux-gnueabihf', 'freebsd', 'openbsd', 'windows-cygnus', 'windows-gnu', 'windows-msvc', 'linux-android', 'linux-androideabi']):
   target_mandates_stable_abi = "TRUE"
   config.available_features.add('swift_only_stable_abi')