Add a --multiroot-data-file option to build sourcekit-lsp in a unified build

Author: ahoppen

Utilities/build-script-helper.py

@@ -73,6 +73,9 @@ def get_swiftpm_options(swift_exec: str, args: argparse.Namespace) -> List[str]:
         '--configuration', args.configuration,
     ]
 
+    if args.multiroot_data_file:
+        swiftpm_args += ['--multiroot-data-file', args.multiroot_data_file]
+
     if args.verbose:
         swiftpm_args += ['--verbose']
 
@@ -247,6 +250,7 @@ def add_common_args(parser: argparse.ArgumentParser) -> None:
         parser.add_argument('--verbose', '-v', action='store_true', help='enable verbose output')
         parser.add_argument('--cross-compile-host', help='cross-compile for another host instead')
         parser.add_argument('--cross-compile-config', help='an SPM JSON destination file containing Swift cross-compilation flags')
+        parser.add_argument('--multiroot-data-file', help='path to an Xcode workspace to create a unified build of all of Swift\'s SwiftPM projects')
 
     if sys.version_info >= (3, 7, 0):
         subparsers = parser.add_subparsers(title='subcommands', dest='action', required=True, metavar='action')