Update python-flit-core to version 3.7.1 / rev 10 via SR 992386
https://build.opensuse.org/request/show/992386
by user bnavigator + dimstar_suse
- Use prjconf provided primary_python if available
- Split primary flavor in multibuild for possible inclusion into
Ring0
- Remove devendoring of tomli, so that we can put this in Ring0