This allows us to install everything in the same dnf command instead
of having to use a prepare script to run dnf from within the image.
This is a hack until mkosi supports release specific dropin files.
Let's make sure we're testing unprivileged builds properly. Usage
of SourceFileTransfer= and SourceFileTransferFinal= are removed as
they were dropped by mkosi. SourceFileTransfer=mount is now the
default in mkosi so behavior for the build script is unchanged. We
stop copying sources in the final image until mkosi adds support
for virtiofs.
It's still useful to test the EFI handover logic in systemd-boot.
We use a mkosi.prepare script to install a newer python and update
the system to use it.