build: only download gn binary for lint step

.circleci/config.yml

@@ -513,10 +513,9 @@ steps-lint: &steps-lint
         name: Download GN Binary
         command: |
           chromium_revision="$(grep -A1 chromium_version src/electron/DEPS | tr -d '\n' | cut -d\' -f4)"
-          buildtools_revision="$(curl -sL "https://chromium.googlesource.com/chromium/src/+/${chromium_revision}/DEPS?format=TEXT" | base64 -d | grep buildtools_revision -A1 | tr -d '\n' | cut -d\' -f4)"
 
-          git clone https://chromium.googlesource.com/chromium/src/buildtools "buildtools"
-          (cd "buildtools" && git checkout "$buildtools_revision")
+          mkdir -p "buildtools/linux64"
+          curl -sL "https://chromium.googlesource.com/chromium/src/+/${chromium_revision}/buildtools/linux64/gn.sha1?format=TEXT" | base64 -d > "buildtools/linux64/gn.sha1"
           echo 'export CHROMIUM_BUILDTOOLS_PATH="'"$PWD"'/buildtools"' >> $BASH_ENV
 
           download_from_google_storage --bucket chromium-gn -s "buildtools/linux64/gn.sha1"