.github: use docker build in release workflow

The release workflow previously called 'make release' to produce the
release artifacts. This commit changes the workflow to first build our
helper Docker image and then use it to produce the release artifacts,
ensuring they're constructed in a consistent environment that can be
easily reproduced outside of CI.

Building the Docker image here adds on perhaps 2-3 minutes to the
workflow, but release workflows are performed very infrequently (only
on a v* tag push) . Note also that this eliminates a location where Go
toolchain version state needs to be tracked.

Author: jtobin

.github/workflows/release.yaml

@@ -37,16 +37,16 @@ jobs:
             exit 1
           fi
 
-      - name: setup go ${{ env.GO_VERSION }}
-        uses: actions/setup-go@v5
-        with:
-          go-version: '${{ env.GO_VERSION }}'
-
       - name: checkout release tag
         run: git checkout ${{ env.RELEASE_VERSION }}
 
+      - name: build release helper docker image
+        run: |
+          docker build -t taproot-assets-release-helper \
+            -f make/builder.Dockerfile make/
+
       - name: build release for all architectures
-        run: make release tag=${{ env.RELEASE_VERSION }}
+        run: make docker-release tag=${{ env.RELEASE_VERSION }}
 
       - name: Create Release
         uses: lightninglabs/gh-actions/action-gh-release@2024.07.24.00