Allow specifying build platforms

Author: aplr

.github/workflows/build.yml

@@ -23,9 +23,13 @@ on:
         required: false
       build-arm:
         type: boolean
-        description: "Enable aarch64 build"
+        description: "Enable aarch64 build. If specified, `platforms` takes precedence over `build-arm`."
         required: false
         default: true
+      platforms:
+        type: string
+        description: "Specify build platforms. Takes precedence over `build-arm`."
+        required: false
     secrets:
       build-secrets:
         description: "The Docker secrets to use for the build"
@@ -83,7 +87,7 @@ jobs:
           context: ${{ inputs.build-context || '.'}}
           target: ${{ inputs.build-target }}
           push: ${{ (github.event_name == 'push' && (github.ref_name == github.event.repository.default_branch || github.ref_type == 'tag')) || github.event_name == 'pull_request' }}
-          platforms: ${{ inputs.build-arm && github.ref_name == github.event.repository.default_branch && 'linux/amd64,linux/arm64' || 'linux/amd64' }}
+          platforms: ${{ inputs.platforms && inputs.platforms || (inputs.build-arm && github.ref_name == github.event.repository.default_branch && 'linux/amd64,linux/arm64' || 'linux/amd64') }}
           provenance: false
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}