swrast_legacy: fix gcc2 GL rendering

* hrev45297 removed the setting of the defines
  in addition to removing the --no-warnings
* Found after a git bisect and stpere's sharp eyes
* Finally resolves #9473

src/add-ons/opengl/swrast_legacy/Jamfile

@@ -20,6 +20,8 @@ if $(TARGET_PLATFORM) != haiku {
 	} else if $(TARGET_ARCH) = sparc {
 		defines += USE_SPARC_ASM ;
 	}
+
+	SubDirC++Flags [ FDefines $(defines) ] ;
 }