Remove signature in build script

Note that this is a temporary solution because `--remote-signature` is
an undocumented option and subject to removal.

(cherry picked from commit 12e8a72)

Tools/build_for_release.py

@@ -96,6 +96,9 @@ def main(argv):
     )
     shutil.copytree(source_app_path, APP_NAME)
 
+    # TODO: find a better way because this is private API
+    execute('codesign', '--remove-signature', APP_NAME)
+
     # Zip.
     with zipfile.ZipFile(ZIP_NAME, 'w') as f:
         archive_dir(f, APP_NAME)