experiment with sccache

.github/workflows/build_test.yml

@@ -8,31 +8,55 @@ on:
     branches:
       - main
 
+env:
+  SCCACHE_GHA_ENABLED: true
+  RUSTC_WRAPPER: sccache
+
 jobs:
   build_all:
     name: Rust project - latest
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-      - uses: actions-rs/toolchain@v1
-        with:
-          toolchain: stable
-
       - name: Install Dependencies
         run: |
           sudo apt-get update -y
           sudo apt-get upgrade -y
           sudo apt-get install libssl-dev openssl -y
 
-      - name: Install rustfmt
-        run: |
-          rustup component add rustfmt
+      - uses: actions/checkout@v4
+
+      # The toolchain action should definitely be run before the cache action
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          # use toolchain version from rust-toolchain.toml
+          components: rustfmt, clippy
+          cache: false
+          # avoid the default "-D warnings" which thrashes cache
+          rustflags: ""
+
+      - name: Run sccache-cache
+        uses: mozilla-actions/sccache-action@v0.0.3
+
+
+      # https://github.com/actions/cache/blob/main/examples.md#rust---cargo
+      - uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cargo/bin/
+#            ~/.cargo/registry/index/
+#            ~/.cargo/registry/cache/
+#            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
 
       - name: Early Build
-        run: cargo build --workspace --tests
+        run: |
+          rustc --version
+          echo $RUSTFLAGS
+          cargo build --workspace --tests
 
-      - name: Check Rust Code Format
-        run:  cargo fmt -- --check
+      - name: Run fmt+clippy
+        run: |
+          cargo fmt --all --check
+          cargo clippy --workspace --all-targets
 
-      - name: Run Rust Clippy
-        run: cargo clippy --all-targets -- -D warnings