update workflow

.github/workflows/build.yml

@@ -5,7 +5,17 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - name: install elan
+        run: |
+          set -o pipefail
+          curl -sSfL https://github.com/leanprover/elan/releases/download/v3.0.0/elan-x86_64-unknown-linux-gnu.tar.gz | tar xz
+          ./elan-init -y --default-toolchain none
+          echo "$HOME/.elan/bin" >> $GITHUB_PATH
+      - uses: actions/checkout@v4
       - uses: actions/setup-node@v3
+      - name: print lean and lake versions
+        run: |
+          lean --version
+          lake --version
       - run: npm install
       - run: npm run build