Migrate to unified core

[Ducky]

There is currently no track for when building without --unified-core will be obsolete, but since it is deprecated, it is worth taking a look at building Sodalite with this flag. Historically this caused problems with Sodalite and hasn't been tried since, but its worth looking at now.

Related:

• coreos/rpm-ostree#729
• fedora-silverblue/issue-tracker#333

[Ducky]

It seems to work properly. Can't see any problems in the OS itself. 🤔

[Ducky]

This is now vital for Sodalite 5 (f38) to build, otherwise it just segfaults. build.sh has been modified in 4dade7b to use --unified-core by default, with --ex-no-unified-core added to disable building with unified core.