[test] Fix macOS triple check

[benlangmuir]

Summary

While the inferred host triple for macOS is something like
<arch>-apple-darwin, it's also valid to have <arch>-apple-macos.
Currently that globally changes whether an SDKROOT is provided in tests,
so make this check more portable.

llvm/utils/lit/lit/util.py

def executeCommand(command, cwd=None, env=None, input=None, timeout=0,
 
     # Detect Ctrl-C in subprocess.
     if exitCode == -signal.SIGINT:
         raise KeyboardInterrupt
 
     return out, err, exitCode
 
 
+def isMacOSTriple(target_triple):
+    """Whether the given target triple is for macOS,
+       e.g. x86_64-apple-darwin, arm64-apple-macos
+    """
+    return 'darwin' in target_triple or 'macos' in target_triple
+
+
 def usePlatformSdkOnDarwin(config, lit_config):
     # On Darwin, support relocatable SDKs by providing Clang with a
     # default system root path.
-    if 'darwin' in config.target_triple:
+    if isMacOSTriple(config.target_triple):
         try:
             cmd = subprocess.Popen(['xcrun', '--show-sdk-path', '--sdk', 'macosx'],
                                    stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             out, err = cmd.communicate()
             out = out.strip()
             res = cmd.wait()
         except OSError:
             res = -1
         if res == 0 and out:
             sdk_path = out.decode()
             lit_config.note('using SDKROOT: %r' % sdk_path)
             config.environment['SDKROOT'] = sdk_path
 
 
 def findPlatformSdkVersionOnMacOS(config, lit_config):
-    if 'darwin' in config.target_triple:
+    if isMacOSTriple(config.target_triple):
         try:
             cmd = subprocess.Popen(['xcrun', '--show-sdk-version', '--sdk', 'macosx'],
                                    stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             out, err = cmd.communicate()
             out = out.strip()
             res = cmd.wait()
         except OSError:
             res = -1