Run the license-metadata check in CI.

This will tell you if license-metadata.json is out of date.

Author: jonathanpallant

src/ci/docker/host-x86_64/mingw-check/Dockerfile

@@ -63,6 +63,7 @@ ENV SCRIPT \
            /scripts/validate-toolstate.sh && \
            /scripts/validate-error-codes.sh && \
            reuse --include-submodules lint && \
+           python3 ../x.py test collect-license-metadata && \
            # Runs checks to ensure that there are no issues in our JS code.
            es-check es2019 ../src/librustdoc/html/static/js/*.js && \
            eslint -c ../src/librustdoc/html/static/.eslintrc.js ../src/librustdoc/html/static/js/*.js && \