mesa: Don't use rtasm for Haiku swrast

* We have a symbol conflict as rtasm in
  Mesa collides with rtasm in gallium.
* As us linking gallium and mesa together
  is an edge case, lets just omit the rtasm
  code from Mesa as we should be going
  llvmpipe soon :)

src/mesa/SConscript

@@ -370,7 +370,7 @@ env.Depends(glget_sources, get_hash_header)
 #
 # Assembly sources
 #
-if env['gcc'] and env['platform'] not in ('cygwin', 'darwin', 'windows'):
+if env['gcc'] and env['platform'] not in ('cygwin', 'darwin', 'windows', 'haiku'):
     if env['machine'] == 'x86':
         env.Append(CPPDEFINES = [
             'USE_X86_ASM',