Add CI job for building Alpine-based Docker image (#6959)

.github/workflows/osrm-backend-docker.yml

@@ -6,6 +6,9 @@ on:
 
 jobs:
   publish:
+    strategy:
+      matrix:
+        docker-base-image: ["debian", "alpine"]
     runs-on: ubuntu-latest
     steps:       
       - name: Check out the repo
@@ -53,10 +56,10 @@ jobs:
         with:
           push: true
           platforms: linux/amd64,linux/arm64
-          file: ./docker/Dockerfile
+          file: ./docker/Dockerfile-${{ matrix.docker-base-image }}
           tags: ${{ steps.metadebug.outputs.tags  }}
           build-args: |
-            DOCKER_TAG=${{ join(steps.metadebug.outputs.tags ) }}
+            DOCKER_TAG=${{ join(steps.metadebug.outputs.tags ) }}-${{ matrix.docker-base-image }}
 
 
       - name: Build container image - assertions
@@ -64,10 +67,10 @@ jobs:
         with:
           push: true
           platforms: linux/amd64,linux/arm64
-          file: ./docker/Dockerfile
+          file: ./docker/Dockerfile-${{ matrix.docker-base-image }}
           tags: ${{ steps.metaassertions.outputs.tags  }}
           build-args: |
-            DOCKER_TAG=${{ join(steps.metaassertions.outputs.tags ) }}
+            DOCKER_TAG=${{ join(steps.metaassertions.outputs.tags ) }}-${{ matrix.docker-base-image }}
 
       # build and publish "normal" image as last to get it listed on top
       - name: Build container image - normal
@@ -75,10 +78,7 @@ jobs:
         with:
           push: true
           platforms: linux/amd64,linux/arm64
-          file: ./docker/Dockerfile
-          tags:  ${{ steps.meta.outputs.tags  }}
+          file: ./docker/Dockerfile-${{ matrix.docker-base-image }}
+          tags: ${{ steps.meta.outputs.tags  }}
           build-args: |
-            DOCKER_TAG=${{ join(steps.meta.outputs.tags ) }}            
-
-
-            
+            DOCKER_TAG=${{ join(steps.meta.outputs.tags ) }}-${{ matrix.docker-base-image }}