build: stop rebuilding the Flatpak dependencies on every run (#15501)

.github/workflows/build_all.yml

@@ -279,20 +279,24 @@ jobs:
         echo "date=$(date +'%Y%m%d')" >> $GITHUB_ENV
         echo "git_commit_hash=$git_commit_hash" >> $GITHUB_ENV
       shell: bash
+    - name: Compute the flatpak-builder cache key
+      id: fp_cache_key
+      run: echo "key=flatpak-builder-${{ matrix.variant.arch }}-${{ hashFiles('deps/**', 'scripts/flatpak/com.orcaslicer.OrcaSlicer.yml', 'scripts/flatpak/make_deps_tar.sh') }}" >> "$GITHUB_OUTPUT"
+      shell: bash
     # Manage flatpak-builder cache externally so PRs restore but never upload
     - name: Restore flatpak-builder cache
       if: github.event_name == 'pull_request'
       uses: actions/cache/restore@v6
       with:
         path: .flatpak-builder
-        key: flatpak-builder-${{ matrix.variant.arch }}-${{ github.event.pull_request.base.sha }}
+        key: ${{ steps.fp_cache_key.outputs.key }}
         restore-keys: flatpak-builder-${{ matrix.variant.arch }}-
     - name: Save/restore flatpak-builder cache
       if: github.event_name != 'pull_request'
       uses: actions/cache@v6
       with:
         path: .flatpak-builder
-        key: flatpak-builder-${{ matrix.variant.arch }}-${{ github.sha }}
+        key: ${{ steps.fp_cache_key.outputs.key }}
         restore-keys: flatpak-builder-${{ matrix.variant.arch }}-
     - name: Disable debug info for faster CI builds
       run: |
@@ -304,6 +308,12 @@ jobs:
         sed -i "/name: OrcaSlicer/{n;s|buildsystem: simple|buildsystem: simple\n    build-options:\n      env:\n        git_commit_hash: \"$git_commit_hash\"|}" \
           scripts/flatpak/com.orcaslicer.OrcaSlicer.yml
       shell: bash
+    - name: Check the manifest keeps orca_deps cacheable
+      run: ./scripts/flatpak/check_manifest_cacheable.sh
+      shell: bash
+    - name: Pack deps/ for the Flatpak manifest
+      run: ./scripts/flatpak/make_deps_tar.sh
+      shell: bash
     - uses: flatpak/flatpak-github-actions/flatpak-builder@master
       with:
         bundle: OrcaSlicer-Linux-flatpak_${{ env.ver }}_${{ matrix.variant.arch }}.flatpak