Run npm install only when needed

.circleci/config.yml

@@ -108,7 +108,10 @@ jobs:
       - run:
           name: Install deps via npm
           command: |
-           sudo npm install -g npm@6
+           # Only run npm install if the package-lock.json or package.json was changed
+           CHANGED_FILES="$(git diff-tree -r --name-only --no-commit-id ORIG_HEAD HEAD)"
+	         echo "$CHANGED_FILES" | grep --quiet "package.*json" && 
+           sudo npm install -g npm@6 &&
            npm install
       - save_cache:
           key: dependency-cache-{{ checksum "package-lock.json" }}