Don’t clean build directory prior to building

AFAICT cleaning the build directory prior to building was done to work around a bug in SwiftPM at some point. I don’t think that it’s needed anymore.

Author: ahoppen

Utilities/build-script-helper.py

@@ -214,10 +214,6 @@ def handle_invocation(swift_exec: str, args: argparse.Namespace) -> None:
     """
     Depending on the action in 'args', build the package, installs the package or run tests.
     """
-    if not args.no_clean:
-        print('Cleaning ' + args.build_path)
-        shutil.rmtree(args.build_path, ignore_errors=True)
-
     if args.action == 'build':
         build(swift_exec, args)
     elif args.action == 'test':