Needed for the build afterwards.
Also added the cflite Dockerfile to automatic CI builds so changes to it
are checked in pull requests.
Also fixed the tokstyle docker image. It needs clang instead of gcc now.
We can't run this on pull requests because it needs access to the
`SONAR_TOKEN` secret. Perhaps in the future we can make it a
`pull_request_target` workflow, but then we can't use cmake to initialise
the environment, meaning we need to specify the inputs manually.
