pkg-config: upgrade to 0.29.2 and build with internal glib

Building normal glib is a nightmare, at least as long as we
haven't stopped using Python 2, so let's try to avoid it.

This makes bin/pkg-config bigger (GCC 6.3.0):
 old size:  47880
 new size: 573992

With Link Time Optimization, GCC 8.3.0 produces a binary of 154656 bytes.
However, GCC 6.3.0 fails to link so we have to wait.