gallium/dri: always link against shared glapi

gallium/dri: always link against shared glapi

In the early days of Xorg and Mesa we had multiple providers of the
GLAPI. All of those were the ones responsible for dlopening the DRI
module. Hence it was perfectly fine, and actually expected, for the DRI
modules to have unresolved symbols.

Since then we've moved the API to a separate shared library and no other
libraries provide the symbols.

Here comes the picky part:
It's possible that one uses old Xorg (where libglx.so provides the
GLAPI) and new Mesa (with DRI modules linking against libglapi.so).

That should still work, since the the libglx.so symbols will take
precedence over the libglapi.so ones.

I've verified this while running 1.14 series Xorg alongside this (and
next) patch.

It may seem a bit fragile, but that's of reasonably OK since all of the
affected Xorg versions have been EOL for years.

The final one being the 1.14 series, which saw its final bug fix release
1.14.7 in June 2014.

To ensure that the binaries do not have unresolved symbols add
-no-undefined and $(LD_NO_UNDEFINED), just like we do everywhere else
throughout mesa.

Cc: mesa-stable@lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98428
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>