Merge pull request swiftlang#29283 from atrick/show-build-targets

Add the target list to build-script --help.

Author: atrick

utils/build_swift/build_swift/driver_arguments.py

@@ -525,8 +525,10 @@ def create_argument_parser():
     option('--stdlib-deployment-targets', store,
            type=argparse.ShellSplitType(),
            default=None,
-           help='list of targets to compile or cross-compile the Swift '
-                'standard library for. %(default)s by default.')
+           help='The targets to compile or cross-compile the Swift standard '
+                'library for. %(default)s by default.'
+                ' Comma separated list: {}'.format(
+                    ' '.join(StdlibDeploymentTarget.get_target_names())))
 
     option('--build-stdlib-deployment-targets', store,
            type=argparse.ShellSplitType(),

utils/swift_build_support/swift_build_support/targets.py

@@ -244,6 +244,11 @@ def get_target_for_name(cls, name):
     def get_targets_by_name(cls, names):
         return [cls.get_target_for_name(name) for name in names]
 
+    @classmethod
+    def get_target_names(cls):
+        return sorted([name for (name, target) in
+                       cls._targets_by_name.items()])
+
 
 def install_prefix():
     """