Multiarch CI image for FIPS builds

Relates to gitlab-org/gitlab#375324 (closed).

There are no 32 bit arm images, so we are not going to have FIPS builds for that architecture.

docker run --platform linux/arm/v7 --rm -it registry.access.redhat.com/ubi8/ubi:8.6   
Unable to find image 'registry.access.redhat.com/ubi8/ubi:8.6' locally
8.6: Pulling from ubi8/ubi
docker: no matching manifest for linux/arm/v7 in the manifest list entries.
See 'docker run --help'.

docker run --platform linux/arm/v6 --rm -it registry.access.redhat.com/ubi8/ubi:8.6
Unable to find image 'registry.access.redhat.com/ubi8/ubi:8.6' locally
8.6: Pulling from ubi8/ubi
docker: no matching manifest for linux/arm/v6 in the manifest list entries.
See 'docker run --help'.