Enable ccache within CI (#26121)

.github/workflows/ci_build_major_branch_keymap.yml

@@ -38,17 +38,18 @@ jobs:
         run: pip3 install -r requirements-dev.txt
 
       - name: Generate build targets
+        shell: 'bash {0}'
         id: generate_targets
         run: |
           { # Intentionally use `shuf` here so that we share manufacturers across all build groups -- some have a lot of ARM-based boards which inherently take longer
             counter=0
             echo -n '{'
-            qmk find -km ${{ inputs.keymap }} 2>/dev/null | sort | uniq | shuf | xargs -L${{ inputs.slice_length }} | while IFS=$'\n' read target ; do
+            qmk find -km ${{ inputs.keymap }} 2>/dev/null | sort | uniq | shuf --random-source=<(openssl enc -aes-256-ctr -pass pass:qmk -nosalt </dev/zero 2>/dev/null) | xargs -L${{ inputs.slice_length }} | while IFS=$'\n' read target ; do
                 if [ $counter -gt 0 ]; then
                     echo -n ','
                 fi
                 counter=$((counter+1))
-                printf "\"group %02d\":{" $counter
+                printf "\"group-%02d\":{" $counter
                 echo -n '"targets":"'
                 echo $target | tr ' ' '\n' | sort | uniq | xargs echo -n
                 echo -n '"}'
@@ -72,6 +73,9 @@ jobs:
     container: ghcr.io/qmk/qmk_cli
     continue-on-error: true
 
+    env:
+      CCACHE_CONFIGPATH: ~/.cache
+
     strategy:
       matrix:
         target: ${{ fromJson(needs.generate_targets.outputs.targets) }}
@@ -83,6 +87,8 @@ jobs:
 
       - name: Checkout QMK Firmware
         uses: actions/checkout@v6
+        with:
+          submodules: recursive
 
       - name: Install dependencies
         run: pip3 install -r requirements-dev.txt
@@ -93,24 +99,43 @@ jobs:
           name: targets-${{ inputs.keymap }}
           path: .
 
-      - name: Deploy submodules
-        run: |
-          qmk git-submodule -f
-
       - name: Dump targets
         run: |
           jq -r '.["${{ matrix.target }}"].targets' targets.json | tr ' ' '\n' | sort
 
+      - name: Restore Cache
+        id: cache
+        uses: actions/cache/restore@v5
+        with:
+          path: ${{ env.CCACHE_CONFIGPATH }}
+          key: compile-${{ inputs.keymap }}-${{ matrix.target }}
+
       - name: Build targets
         continue-on-error: true
         run: |
-          export NCPUS=$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || getconf _NPROCESSORS_ONLN 2>/dev/null) -1 ))
           targets=$(jq -r '.["${{ matrix.target }}"].targets' targets.json | tr ' ' '\n' | sort)
           if [ -z "${targets}" ]; then
             echo "Zero build targets detected"
             exit 0
           fi
-          qmk mass-compile -t -j $NCPUS -e DUMP_CI_METADATA=yes $targets || touch .failed
+          qmk mass-compile -t -j $(nproc) -e DUMP_CI_METADATA=yes -e USE_CCACHE=yes $targets || touch .failed
+
+      - name: Dump ccache stats
+        run: |
+          ccache -s
+
+      # Delete the old cache on hit to emulate a cache update. See https://github.com/actions/cache/issues/342.
+      - name: Delete old cache
+        env:
+          GH_TOKEN: ${{ github.token }}
+        if: steps.cache.outputs.cache-hit
+        run: gh cache delete --ref ${{ github.ref }} ${{ steps.cache.outputs.cache-primary-key }}
+
+      - name: Save Cache
+        uses: actions/cache/save@v5
+        with:
+          path: ${{ env.CCACHE_CONFIGPATH }}
+          key: compile-${{ inputs.keymap }}-${{ matrix.target }}
 
       - name: Upload binaries
         uses: actions/upload-artifact@v7