Respect the TOOLCHAINS environment variable if set when deciding the darwin xcrun toolchain.

Author: Rostepher

utils/build-script

@@ -1041,6 +1041,11 @@ def main_normal():
     shell.dry_run = args.dry_run
 
     # Prepare and validate toolchain
+    env_toolchain = os.environ.get('TOOLCHAINS')
+    if args.darwin_xcrun_toolchain is None:
+        diagnostics.note('using toolchain {}'.format(env_toolchain))
+        args.darwin_xcrun_toolchain = env_toolchain
+
     toolchain = host_toolchain(xcrun_toolchain=args.darwin_xcrun_toolchain)
     os.environ['TOOLCHAINS'] = args.darwin_xcrun_toolchain
 

utils/build_swift/driver_arguments.py

@@ -317,7 +317,6 @@ def create_argument_parser():
            help='the number of parallel build jobs to use')
 
     option('--darwin-xcrun-toolchain', store,
-           default=defaults.DARWIN_XCRUN_TOOLCHAIN,
            help='the name of the toolchain to use on Darwin')
     option('--cmake', store_path(executable=True),
            help='the path to a CMake executable that will be used to build '

utils/build_swift/tests/expected_options.py

@@ -106,8 +106,7 @@
         defaults.DARWIN_DEPLOYMENT_VERSION_TVOS,
     'darwin_deployment_version_watchos':
         defaults.DARWIN_DEPLOYMENT_VERSION_WATCHOS,
-    'darwin_xcrun_toolchain':
-        defaults.DARWIN_XCRUN_TOOLCHAIN,
+    'darwin_xcrun_toolchain': None,
     'distcc': False,
     'dry_run': False,
     'enable_asan': False,