Pre-install browser-ui-test in x86_64-gnu-tools Dockerfile

Author: Kobzol

src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile

@@ -99,7 +99,9 @@ COPY scripts/shared.sh /scripts/
 #
 # The `browser-ui-test.version` file is also used by bootstrap to emit warnings in case
 # the local version of the package is different than the one used by the CI.
+
+RUN bash -c 'npm install -g browser-ui-test@$(head -n 1 /tmp/browser-ui-test.version) --unsafe-perm=true'
+
 ENV SCRIPT /tmp/checktools.sh ../x.py && \
-  npm install browser-ui-test@$(head -n 1 /tmp/browser-ui-test.version) --unsafe-perm=true && \
   python3 ../x.py check compiletest --set build.compiletest-use-stage0-libtest=true && \
   python3 ../x.py test tests/rustdoc-gui --stage 2 --test-args "'--jobs 1'"