All Gentoo builds are failing with `Multiple package instances within a single package slot have been pulled into the dependency graph, resulting in a slot conflict`

@ijansky @mgomersbach I was preparing some further updates for this repo and I found that all of the Gentoo builds are failing with the same error Multiple package instances within a single package slot have been pulled into the dependency graph, resulting in a slot conflict:

• gent-late-master-py3: https://gitlab.com/myii/salt-image-builder/-/jobs/903200710#L257
• gent-sysd-master-py3: https://gitlab.com/myii/salt-image-builder/-/jobs/903200714#L255

Also noticed the following error further above, not sure how significant it is:

+ emerge-webrsync
!!! Section 'gentoo' in repos.conf has location attribute set to nonexistent directory: '/var/db/repos/gentoo'
!!! Invalid Repository Location (not a dir): '/var/db/repos/gentoo'

This is the link to all of the builds that failed during that pipeline:

• https://gitlab.com/myii/salt-image-builder/-/pipelines/228004752/failures

I expect this to start affecting our weekly builds from tomorrow; if there's no quick fix, that's not a big deal -- we'll just comment out all of the Gentoo builds for the time being. The last images are still available in Docker Hub.