ci: use sccache

We install sccache using cargo and cache its binary to avoid this
overhead on subsequent invocations.

We start an sccache server before building and stop it afterwards,
printing stats before doing so.

We also set environment variables to point sccache at an S3 bucket
that I control. I manually installed secrets with an AWS access key
with read/write access to just the key prefix in this bucket.

.github/workflows/pyoxidizer.yml

@@ -20,9 +20,13 @@ jobs:
     runs-on: ${{ matrix.os }}
     env:
       IN_CI: '1'
+      AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
+      AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
+      SCCACHE_BUCKET: 'gregoryszorc-ci-pyoxidizer-sccache'
+      SCCACHE_S3_USE_SSL: '1'
     steps:
       - name: Install Linux system packages
-        if: ${{ runner.os == 'Linux' }}
+        if: runner.os == 'Linux'
         run: |
           sudo apt-get install -y libyaml-dev snapcraft
 
@@ -44,17 +48,67 @@ jobs:
           profile: minimal
           target: x86_64-unknown-linux-musl
 
+      - name: Cache sccache (Windows)
+        id: cache-sccache-windows
+        if: runner.os == 'Windows'
+        uses: actions/cache@v2
+        with:
+          path: C:/Rust/.cargo/bin/sccache.exe
+          key: ${{ runner.os }}-sccache-0
+
+      - name: Install sccache build dependencies (Windows)
+        if: runner.os == 'Windows' && steps.cache-sccache-windows.outputs.cache-hit != 'true'
+        run: |
+          vcpkg integrate install
+          vcpkg install openssl:x64-windows
+
+      - name: Install sccache (Linux)
+        if: runner.os == 'Linux'
+        run: |
+          wget -O sccache.tar.gz https://github.com/mozilla/sccache/releases/download/0.2.13/sccache-0.2.13-x86_64-unknown-linux-musl.tar.gz
+          tar -xvzf sccache.tar.gz
+          mv sccache-0.2.13-x86_64-unknown-linux-musl/sccache /usr/share/rust/.cargo/bin/sccache
+
+      - name: Install sccache (macOS)
+        if: runner.os == 'macOS'
+        run: |
+          wget -O sccache.tar.gz https://github.com/mozilla/sccache/releases/download/0.2.13/sccache-0.2.13-x86_64-apple-darwin.tar.gz
+          tar -xvzf sccache.tar.gz
+          mv sccache-0.2.13-x86_64-apple-darwin/sccache /Users/runner/.cargo/bin/sccache
+
+      - name: Install sccache (Windows)
+        if: steps.cache-sccache-windows.outputs.cache-hit != 'true' && runner.os == 'Windows'
+        # sccache doesn't work with Rust 1.48. https://github.com/mozilla/sccache/issues/887
+        run: |
+          rustup install 1.47.0
+          cargo +1.47.0 install --features 'azure s3' sccache
+
+      - name: Start sccache
+        run: |
+          sccache --start-server
+
       # TODO get pyembed working. It needs a working libpython.
       - name: Build Workspace
+        env:
+          RUSTC_WRAPPER: sccache
         run: |
           cargo build --workspace --exclude pyembed --exclude oxidized-importer
           cargo run --bin pyoxidizer -- --version
 
       - name: Test Workspace
+        env:
+          RUSTC_WRAPPER: sccache
         run: |
           cargo test --workspace --exclude pyembed --exclude oxidized-importer
 
       - name: Run Clippy
         if: ${{ matrix.rust_toolchain == 'stable' || matrix.rust_toolchain == 'beta' }}
+        env:
+          RUSTC_WRAPPER: sccache
         run: |
           cargo clippy --workspace --exclude pyembed --exclude oxdized-importer
+
+      - name: Stop sccache
+        run: |
+          sccache --show-stats
+          sccache --stop-server