Manually set cache directory path when running GUI tests

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

@@ -78,16 +78,6 @@ ENV PATH="$NODE_FOLDER:${PATH}"
 
 COPY host-x86_64/x86_64-gnu-tools/browser-ui-test.version /tmp/
 
-# For now, we need to use `--unsafe-perm=true` to go around an issue when npm tries
-# to create a new folder. For reference:
-# https://github.com/puppeteer/puppeteer/issues/375
-#
-# We also specify the version in case we need to update it to go around cache limitations.
-#
-# 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 npm install -g browser-ui-test@$(head -n 1 /tmp/browser-ui-test.version) --unsafe-perm=true
-
 ENV RUST_CONFIGURE_ARGS \
   --build=x86_64-unknown-linux-gnu \
   --save-toolstates=/tmp/toolstate/toolstates.json \
@@ -100,6 +90,14 @@ COPY host-x86_64/dist-x86_64-linux/build-gccjit.sh /scripts/
 
 RUN /scripts/build-gccjit.sh /scripts
 
+# For now, we need to use `--unsafe-perm=true` to go around an issue when npm tries
+# to create a new folder. For reference:
+# https://github.com/puppeteer/puppeteer/issues/375
+#
+# We also specify the version in case we need to update it to go around cache limitations.
+#
+# 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.
 ENV SCRIPT /tmp/checktools.sh ../x.py && \
-  NODE_PATH=`npm root -g` python3 ../x.py test tests/rustdoc-gui --stage 2 \
-    --test-args "'--no-sandbox --jobs 1'"
+  npm install browser-ui-test@$(head -n 1 /tmp/browser-ui-test.version) --unsafe-perm=true && \
+  python3 ../x.py test tests/rustdoc-gui --stage 2 --test-args "'--no-sandbox --jobs 1'"