scons: Fix SCons build infrastructure for FreeBSD.

This patch gets the FreeBSD SCons build working again. The build still
fails though.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/SConscript

@@ -22,7 +22,7 @@ SConscript('mesa/SConscript')
 SConscript('mapi/vgapi/SConscript')
 
 if not env['embedded']:
-    if env['platform'] not in ('cygwin', 'darwin', 'haiku', 'windows'):
+    if env['platform'] not in ('cygwin', 'darwin', 'freebsd', 'haiku', 'windows'):
         SConscript('glx/SConscript')
     if env['platform'] not in ['darwin', 'haiku', 'sunos']:
         SConscript('egl/main/SConscript')