Revert "[conf] remove duplicates after setting all flags and sources"
Doesn't work as intended (yet).
The sorting e.g. splits up `pkg-config glib-2.0 --cflags` into
--cflags` glib-2.0 `pkg-config
so it doesn't work anymore...
One way could be to make sure to resolve these first before sorting.

This reverts commit 70168207abc7f5c2b6a0fc766e03e8bf2b633009.