message: build-backend.sh: use SOURCE_GIT_TAG if available
  This will be supplied in downstream builds to relay the tag from the source git repo.
diff: @@ -7,7 +7,7 @@ set -e
  PROJECT_DIR=$(basename ${PWD})
  -GIT_TAG=`git describe --always --tags HEAD`
  +GIT_TAG=${SOURCE_GIT_TAG:-$(git describe --always --tags HEAD)}
  LD_FLAGS="-w -X github.com/openshift/console/version.Version=${GIT_TAG}"
  CGO_ENABLED=0 go build -ldflags "${LD_FLAGS}" -o bin/bridge github.com/openshift/console/cmd/bridge
  