scons: Support clang.
clang is supports most gcc options / extensions, with a some exceptions.
The biggest advantage of using clang is that compilation times are much
short.
One can tell scons to use clang when building by invoking it as
CC=clang CXX=clang++ scons libgl-xlib
diff --git a/src/mesa/SConscript b/src/mesa/SConscript
index 3cd0f87..15b6269 100644
--- a/src/mesa/SConscript
+++ b/src/mesa/SConscript
@@ -351,7 +351,8 @@
#
# Assembly sources
#
-if env['gcc'] and env['platform'] not in ('cygwin', 'darwin', 'windows', 'haiku'):
+if (env['gcc'] or env['clang']) and \
+ env['platform'] not in ('cygwin', 'darwin', 'windows', 'haiku'):
if env['machine'] == 'x86':
env.Append(CPPDEFINES = [
'USE_X86_ASM',