fix: specify ENV build arg

Author: wdconinc

.github/workflows/build-push.yml

@@ -224,6 +224,7 @@ jobs:
             KEY4HEPSPACK_VERSION=${{ steps.key4hep-spack.outputs.version }}
             S3_ACCESS_KEY=${{ secrets.S3_ACCESS_KEY }}
             S3_SECRET_KEY=${{ secrets.S3_SECRET_KEY }}
+            ENV=${{ matrix.ENV }}
             jobs=${{ env.JOBS }}
           cache-from: type=gha,scope=${{ github.workflow }}
           cache-to: type=gha,mode=max,scope=${{ github.workflow }}