Hi,
In the pkg-config files( /usr/lib/pkgconfig/gl.pc etc.),
the prefix is set as "/home/jan/svn/........."
It is a local path of the computer of <jgc at archlinux.org> .
I dare say that is wrong!
When I run "pkg-config gl --cflags", it told me that wrong path.
Would you re-make the packages(mesa libgl) ?
Cheers!