disable nvtt by default, because it is not in portage

--- devil-1.7.8.ebuild
+++ devil-1.7.8.ebuild
@@ -62,7 +62,8 @@
 		$(use_enable sse2) \
 		$(use_enable sse3) \
 		--disable-directx8 \
-		--disable-directx9
+		--disable-directx9 \
+		--with-nvtt=no
 }
 
 src_install() {