See https://bugs.gentoo.org/show_bug.cgi?id=458300 for the problem and possible solution (similar to the one used for OSMesa).
On not quite related note: it would seem constructs like 'AC_ARG_ENABLE([xlib_glx],' aren't quite correct - to match AS_HELP_STRING, they should be 'AC_ARG_ENABLE([xlib-glx],', cause while the corect var to check for will have an underscore, '--enable-FEATURE' string takes FEATURE from first argument of the macro.
Created attachment 75240 [details] [review]
Does this patch help?
(In reply to comment #1)
> Created attachment 75240 [details] [review] [review]
> possible fix
> Does this patch help?
Well, it should help - that's exactly the solution I've proposed.
On the other hand, I'm not the original reporter - I've only moved it here, so that 9.1 gets the fix before its release.
The downstream bug has been just been updated - will get back to you.
Fixed by commit c1eb585f3d62670782d9cc73637b7e3bcab46d66
Cherry-picked to the 9.1 branch: be7048477a2989bd11ab590c65ea1515f764a86c
It will be available in Mesa 9.1
Please reopen the bug if the problem still exists.