~xc/config/cf/xf86site.def.
~xc/config/cf/xf86site.def.
You should also make certain your version of GCC predefines `sun'.
2.4.5 is known NOT to by default.  If needed edit
/usr/local/lib/gcc-lib/*/*/specs, and modify the
*predefines: line.
Note: A Threaded Xlib compiled with GCC has subtle problems. It'll work 98% of the time, however clients will occasionally exhibit strange hangs. Most notably image viewers such as xv-3.10 exhibit this problem.
It is recommended that you set ThreadedX in
~xc/config/cf/sun.cf to NO, if you are using GCC.
ProWorks does not have this problem.
With XFree86 3.3.2, you will need to setup a /opt/SUNWspro/bin
directory containing symbolic links named cc, CC, and
c++filt pointing respectively to the actual gcc,
g++ and c++filt commands.
~xc/config/cf/host.def.
/opt/SUNWspro/bin
/usr/ccs/bin
at the front of your PATH. There are known 
problems with some GNU replacements for the utilities found there. So 
the /usr/ccs/bin versions of these programs 
must be found before any 
other possible GNU versions. (Most notably GNU 'ar' does not work 
during the build).
You  need to set HasSolx86apertureDrv to YES in 
~xc/config/cf/xf86site.def.
to enable the aperture driver.
Under Solaris 2.5 and later, there's a system driver
(/dev/xsvc that provides this functionality. It will
be detected automatically by the server, so you don't need to
install the driver.
For Solaris 2.1 and 2.4, the source for this driver is included in 
~xc/programs/Xserver/hw/xfree86/etc/apSolx86.shar.  
Building, and 
installing the driver is relatively straight forward. Please read 
its accompanying README file.