CI: kernel: use ccache to speedup workflow

Use ccache to speedup kernel compilation.
Ccache dir is cached across each build test. To refresh ccache directory
we generate an hash of the kernel include files, that includes the
kernel versions of every kernel supported and the kernel compile
includes.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
(cherry picked from commit 137ba15e6ef31534a2002a02e69b774232f0b040)

diff --git a/.github/workflows/kernel.yml b/.github/workflows/kernel.yml
index c04e240192d2cc5caa8bd7065d6562f0739ed1f1..99b8aefbe1d46c82eb750dc646d65a072c5488fc 100644 (file)
--- a/.github/workflows/kernel.yml
+++ b/.github/workflows/kernel.yml
@@ -14,6 +14,7 @@ jobs:
     outputs:
       target: ${{ steps.find_targets.outputs.target }}
       owner_lc: ${{ steps.lower_owner.outputs.owner_lc }}
+      ccache_hash: ${{ steps.ccache_hash.outputs.ccache_hash }}
 
     steps:
       - name: Checkout
@@ -26,6 +27,13 @@ jobs:
             | tr '[:upper:]' '[:lower:]')
           echo "::set-output name=owner_lc::$OWNER_LC"
 
+      - name: Generate ccache hash
+        id: ccache_hash
+        run: |
+          CCACHE_HASH=$(md5sum include/kernel-* | awk '{ print $1 }' \
+           | md5sum | awk '{ print $1 }')
+          echo "::set-output name=ccache_hash::$CCACHE_HASH"
+
       - name: Set targets
         id: find_targets
         run: |
@@ -129,6 +137,14 @@ jobs:
           path: openwrt/${{ env.TOOLCHAIN_FILE }}
           key: ${{ env.TOOLCHAIN_FILE }}-${{ env.TOOLCHAIN_SHA256 }}
 
+      - name: Cache ccache
+        uses: actions/cache@v3
+        with:
+          path: openwrt/.ccache
+          key: ccache-kernel-${{ env.TARGET }}/${{ env.SUBTARGET }}-${{ needs.determine_targets.outputs.ccache_hash }}
+          restore-keys: |
+            ccache-kernel-${{ env.TARGET }}/${{ env.SUBTARGET }}-
+
       - name: Download external toolchain
         if: ${{ steps.cache-external-toolchain.outputs.cache-hit != 'true' }}
         shell: su buildbot -c "sh -e {0}"
@@ -149,6 +165,7 @@ jobs:
           echo CONFIG_ALL_KMODS=y >> .config
           echo CONFIG_DEVEL=y >> .config
           echo CONFIG_AUTOREMOVE=y >> .config
+          echo CONFIG_CCACHE=y >> .config
 
           ./scripts/ext-toolchain.sh \
             --toolchain ${{ env.TOOLCHAIN_FILE }}/toolchain-* \