Releasing `loki-build-image`

The loki-build-image is the Docker image used to run tests and build Loki binaries in CI.

How To Perform a Release

Update BUILD_IMAGE_VERSION in the Makefile
Update the image version in all the other places it exists
1. Dockerfiles in cmd directory
2. .circleci/config.yml
Run make drone to rebuild the drone yml file with the new image version (the image version in the Makefile is used)
Commit your changes (else you will get a WIP tag)
Run make build-image-push