build: Don't overlink gallium xlib target

build: Don't overlink gallium xlib target

Currently gallium's xlib target will fail to link due to multiple
definitions of all the symbols in libmesautil, this only shows up in
autotools, and not in meson due to differences in the way that meson and
autotools handle linking static archives into static archives. Autotools
uses -Wl,--whole-archive implicitly, meson requires this behavior to be
opted-into. The solution is just to remove libmesautils from the
libgl-xlib target, since it will get all of those symbols form
libmesagallium.

I've dropped the link from meson as well, it doesn't seem to hurt
anything and should make linking just a little faster.

Fixes: 8396043f304bb2a752130230055605c5c966e89f
       ("Replace uses of _mesa_bitcount with util_bitcount")
bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107923
Tested-by: Brian Paul <brianp@vmware.com>
Tested-by: Vinson Lee <vlee@freedesktop.org>
Cc: Sergii Romantsov<sergii.romantsov@globallogic.com>