ci: Add caching of ccache for Zephyr.

Similar to the ESP32 builds, but needs additional step to pass the
ccache directory through to the Zephyr container.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

.github/workflows/ports_zephyr.yml

@@ -42,6 +42,10 @@ jobs:
         # cache the "workspace"
         path: ./zephyrproject
         key: zephyr-workspace-${{ steps.versions.outputs.ZEPHYR }}
+    - name: ccache
+      uses: hendrikmuhs/ccache-action@v1.2
+      with:
+        key: zephyr
     - name: Install packages
       run: source tools/ci.sh && ci_zephyr_setup
     - name: Install Zephyr

tools/ci.sh

@@ -754,12 +754,15 @@ function ci_zephyr_setup {
     # Directories cached by GitHub Actions, mounted
     # into the container
     ZEPHYRPROJECT_DIR="$(pwd)/zephyrproject"
+    CCACHE_DIR="$(pwd)/.ccache"
 
     mkdir -p "${ZEPHYRPROJECT_DIR}"
+    mkdir -p "${CCACHE_DIR}"
 
     docker run --name zephyr-ci -d -it \
       -v "$(pwd)":/micropython \
       -v "${ZEPHYRPROJECT_DIR}":/zephyrproject \
+      -v "${CCACHE_DIR}":/root/.cache/ccache \
       -e ZEPHYR_SDK_INSTALL_DIR=/opt/toolchains/zephyr-sdk-${ZEPHYR_SDK_VERSION} \
       -e ZEPHYR_TOOLCHAIN_VARIANT=zephyr \
       -e ZEPHYR_BASE=/zephyrproject/zephyr \