Makefile.include: process pkg/*/Makefile.include before using BASELIBS

They can define PSEUDOMODULES which is used to populate BASELIBS.
It means they must be processed before using BASELIBS immediate value.

This moved the processing of all `Makefile.include` before using `BASELIBS`.
It is also moved before setting `BASELIBS` in `modules.inc.mk to keep the
order logical (it would work anyway thanks to deferred variables evaluation).

This fixes the problems for `make -C tests/unittests`