ci: save/restore west repositories from cache

Author: pillo79

.github/workflows/package_core.yml

@@ -30,18 +30,25 @@ jobs:
           fetch-depth: 0
           persist-credentials: false
 
+      - name: ccache
+        uses: hendrikmuhs/ccache-action@v1.2
+        with:
+          verbose: 1
+
+      - name: Use west repo cache
+        uses: actions/cache/restore@v4
+        with:
+          path: "**/.git"
+          key: west-git-${{ github.event.repository.updated_at }}
+          partial-key: west-git-
+
       - name: Initialize
         run: |
           ./extra/bootstrap.sh -o=--filter=tree:0
           echo "CORE_TAG=$(git describe --always)" >> "$GITHUB_ENV"
           echo "CORE_ARTIFACT=ArduinoCore-zephyr-$(git describe --always)" >> "$GITHUB_ENV"
           echo "BOARD_NAMES=[ $(cat boards.txt | grep '^[^#]*\.build\.variant' | cut -d '.' -f 1 | xargs printf '"%s",' | sed -e 's/,$//') ]" >> "$GITHUB_ENV"
 
-      - name: ccache
-        uses: hendrikmuhs/ccache-action@v1.2
-        with:
-          verbose: 1
-
       - name: Build variants
         run: |
           ./extra/build_all.sh -f
@@ -57,6 +64,12 @@ jobs:
           name: ${{ env.CORE_ARTIFACT }}
           path: ${{ env.CORE_ARTIFACT }}.tar.bz2
 
+      - name: Save west repo cache
+        uses: actions/cache/save@v4
+        with:
+          path: "**/.git"
+          key: west-git-${{ github.event.repository.updated_at }}
+
   test-core:
     name: Test ${{ matrix.board }} board
     runs-on: ubuntu-latest