remove second cache statement and make yarn command clearer

.github/workflows/bld_docker.yml

@@ -142,15 +142,7 @@ jobs:
           bump: ${{ inputs.bump }}
 
       - uses: docker/setup-buildx-action@v3
-      - uses: actions/cache@v4
-        with:
-          path: /tmp/.buildx-cache
-          # each cache needs a unique key for the job
-          key: ${{ runner.os }}-buildx-${{ hashFiles(inputs.context) }}
-          # Alternative restore keys if no exact match is found
-          # I /think/ this means that other docker buildx jobs could help out here
-          restore-keys: |
-            ${{ runner.os }}-buildx-
+
       - name: Login to private registry
         uses: docker/login-action@v3
         with:

Dockerfile.build.yarn

@@ -6,7 +6,7 @@ WORKDIR /app
 
 COPY package.json .
 
-RUN yarn
+RUN yarn install --frozen-lockfile
 
 COPY *.json .