Xorg 7.1, Mesa, threads

[J. Hart]

It seems that a modular build of Xorg requires that Mesa be installed.  
Installation of Mesa seems to require that Glibc be installed with 
Linuxthreads rather than NPTL.  if, for example, Glibc 2.36 is installed 
with Linuxthreads support, a version of the header file 
"/usr/include/bits/initspin.h" will also be installed with a definition 
of __LOCK_INITIALIZER.  This definition seems to be required to build 
Mesa 6.5.  If NPTL support is specified instead, a stub version of 
initspin.h is given which lacks this definition.  It should also be 
noted that as of Glibc 2.4, Linuxthreads is no longer included.

Does anyone have any ideas on this ?