[openwrt/openwrt] CI: kernel: use ccache to speedup workflow

[LEDE Commits]

ansuel pushed a commit to openwrt/openwrt.git, branch openwrt-22.03:
https://git.openwrt.org/431875b3dfa117cdf051941ad9efc118bba77a44

commit 431875b3dfa117cdf051941ad9efc118bba77a44
Author: Christian Marangi <ansuelsmth at gmail.com>
AuthorDate: Tue Oct 4 18:43:38 2022 +0200

    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 at gmail.com>
    (cherry picked from commit 137ba15e6ef31534a2002a02e69b774232f0b040)
---
 .github/workflows/kernel.yml | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/.github/workflows/kernel.yml b/.github/workflows/kernel.yml
index c04e240192..99b8aefbe1 100644
--- 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 at 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-* \