feat(gha): use sccache

Author: billf

.github/workflows/test.yaml

@@ -7,6 +7,9 @@ on:
 
 jobs:
   tests:
+    env:
+      SCCACHE_GHA_ENABLED: "true"
+      RUSTC_WRAPPER: "sccache"
     strategy:
       matrix:
         os: [ ubuntu-latest-16 ]
@@ -18,6 +21,8 @@ jobs:
       - uses: cachix/cachix-action@v14
         with:
           name: devenv
+      - name: sccache
+        uses: Mozilla-Actions/sccache-action@main
       - uses: Swatinem/rust-cache@v2
         with:
           save-if: ${{ github.ref == 'refs/heads/master' }}