Fix npm install error

Author: GuillaumeGomez

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

@@ -30,7 +30,6 @@ ENV PATH="/node/bin:${PATH}"
 
 # Install eslint
 COPY host-x86_64/mingw-check-tidy/eslint.version /tmp/
-RUN npm install eslint@$(head -n 1 /tmp/eslint.version)
 
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
@@ -44,5 +43,5 @@ COPY host-x86_64/mingw-check/validate-error-codes.sh /scripts/
 
 # NOTE: intentionally uses python2 for x.py so we can test it still works.
 # validate-toolstate only runs in our CI, so it's ok for it to only support python3.
-ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test \
-           --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
+ENV SCRIPT TIDY_PRINT_DIFF=1 npm install eslint@$(head -n 1 /tmp/eslint.version) && \
+ python2.7 ../x.py test --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp