Before there was a licensing conflict between the keyfile code
(libnm-keyfile) and libnm. The latter would require LGPL-2.1+ while
keyfile code was GPL-2.0+.
Consequently we were linking libnm-keyfile into the daemon, but not in
libnm.so.
This conflict has been resolved and keyfile API is part of libnm.so.
There is no more need to build a separate (intermediary) library. Merge
them.
This also makes sense because keyfile code needs access to private code
from libnm-core. It is closely tied to libnm-core, so that building them
separate makes no sense (anymore).
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