workflows/reusable.yaml: Remove uses: action-build-package

Don't use ci/action-build-package@master in actions.yml anylonger, spell its steps out one-by-one in reusable.yaml instead. This makes the step names appear as log section headers in the UI, which is more explicit and, hence, nicer.
This pretty much obsoletes the composite actions.yml. It should be probably removed, and since this changes the point of this repository from providing an action to providing a workflow, it shoud probably be renamed from action-build-package to workflow-build-package or something.
Signed-off-by: Jan Lindemann <jan@janware.com>

.github/workflows/reusable.yaml

@@ -7,6 +7,7 @@ jobs:
   test:
     name: Packaging test - ${{ matrix.distro.name }}
     runs-on: public-ci
+
     strategy:
       fail-fast: false
       matrix:
@@ -18,7 +19,35 @@ jobs:
       image: ${{ matrix.distro.image }}
 
     steps:
-      - name: Run packaging test
-        uses: ci/action-build-package@master
+      - name: Checkout repository
+        uses: ci/action-checkout@main-jw
         with:
-          distro-name: ${{ matrix.distro.name }}
+          path: ${{ github.event.repository.name }}
+          working-directory: ${{ github.event.repository.name }}
+          persist-credentials: false
+
+      - name: Install build prerequisites
+        shell: bash
+        run: |
+          set -euxo pipefail
+          export PROJECTS_DIR_REMOTE_BASE=${{ github.server_url }}
+          owner=janware
+          makefile=$PROJECTS_DIR_REMOTE_BASE/$owner/jw-pkg/raw/branch/master/make/projects-dir-minimal.mk
+          curl --create-dirs -o build-jw-foss/Makefile "$makefile"
+          make -C build-jw-foss pkg-manager-refresh
+          make -C build-jw-foss pkg-install-release-deps
+          OFFLINE=true make -C build-jw-foss pkg-rebuild-reinstall
+
+      - name: Build package
+        shell: bash
+        run: |
+          set -euxo pipefail
+          make -C "${{ github.event.repository.name }}" pkg-manager-refresh
+          make -C "${{ github.event.repository.name }}" pkg-install-testbuild-deps
+          make -C "${{ github.event.repository.name }}" pkg-rebuild
+
+      - name: Install package
+        shell: bash
+        run: |
+          set -euxo pipefail
+          make -C "${{ github.event.repository.name }}" pkg-reinstall