ci: build: harmonize the build job with the ones used in other projects

We have since rolled out out the forrest runner for other projects
(meta-ptx, meta-rauc and meta-labgrid) and have decided to use shared
sstate, git and downloads directories that are updated via rsync at the
end of runs.

This makes the meta-lxatac project a special case and the only one that
persists disk images instead.

Remove this special-casing by also employing the sstate rsyncing logic
for meta-lxatac.

The other projects take extra care to enable running the build process
on public GitHub runners by using an sstate mirror and using that in the
public runner case.
But meta-lxatac's heavy bones make it unlikely that a build will succeed,
event with an sstate mirror, so this extra logic has been left out.

Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>

.github/workflows/build.yml

@@ -16,35 +16,29 @@ jobs:
     runs-on: [self-hosted, forrest, build]
     if: ${{ vars.HAS_BUILD_RUNNER || github.repository == 'linux-automation/meta-lxatac' }}
     steps:
-      - name: Set up runner machine
-        run: |
-          sudo localectl set-locale en_US.UTF-8
-          export DEBIAN_FRONTEND=noninteractive
-          export DPKG_FORCE=confnew
-          sudo -E apt-get update
-          sudo -E apt-get --assume-yes dist-upgrade
-          sudo -E apt-get --assume-yes install build-essential chrpath diffstat gawk git lz4
       - name: Check out the repository
         uses: actions/checkout@v4
-        with:
-          submodules: recursive
-          path: source
-      - name: Build bundle and images
+
+      - name: Check out submodules
         run: |
-          # We clone meta-lxatac and its submodules into a sub-directory to
-          # prevent the checkout action from deleting our build directory.
-          # Keeping the build directory gives us incremental builds,
-          # with all its benefits (speed) and drawbacks (reproducibility).
+          # Doing this by hand allows us to use local clones of the git
+          # projects as reference to speed up the process.
 
-          # Make sure we start with a fresh config.
-          rm -rf build/conf
+          for sub in meta-ptx meta-oe meta-rauc meta-labgrid meta-virtualization poky meta-selinux
+          do
+            git submodule update \
+              --init \
+              --reference "/srv/shared-git/${sub}.git" \
+              -- "${sub}"
+          done
 
+      - name: Build bundle and images
+        run: |
           # oe-init-build-env implicitly cd-s into the build directory.
-          cd source
-          source oe-init-build-env ../build
+          source oe-init-build-env build
 
-          # Save disk space by deleting a packages build directory once built.
-          echo 'INHERIT += "rm_work"' >> conf/local.conf
+          # Apply default config provided by our custom runner images
+          cp ~/.yocto/auto.conf conf/
 
           # Build all images that are relevant to us.
           bitbake \
@@ -54,6 +48,7 @@ jobs:
             emmc-image \
             emmc-boot-image \
             tf-a-stm32mp
+
       - name: Print logs of failed jobs
         if: ${{ failure() }}
         shell: python3 {0}
@@ -72,10 +67,14 @@ jobs:
               print(f'::group::Contents of "{shorter_path}"')
               print(open(path).read())
               print('::endgroup::')
-      - name: Persist the disk image
+
+      - name: Cache Data
         env:
-          PERSISTENCE_TOKEN: ${{ secrets.PERSISTENCE_TOKEN }}
-        if: ${{ github.ref_protected && env.PERSISTENCE_TOKEN != '' }}
+          CACHE_KEY: ${{ secrets.YOCTO_CACHE_KEY }}
+        if: ${{ github.ref_protected && env.CACHE_KEY }}
         run: |
-          sudo fstrim /
-          echo "$PERSISTENCE_TOKEN" > ~/config/persist
+          mkdir -p ~/.ssh
+          echo "$CACHE_KEY" >> ~/.ssh/id_ed25519
+          chmod 600 ~/.ssh/id_ed25519
+          rsync -rvx --ignore-existing build/downloads yocto-cache: || true
+          rsync -rvx --ignore-existing build/sstate-cache yocto-cache: || true