devdraw: default to native gui on OS X

src/cmd/devdraw/mkwsysrules.sh

diff --git a/src/cmd/devdraw/mkwsysrules.sh b/src/cmd/devdraw/mkwsysrules.sh
index 1239b86..88102c8 100644
--- a/src/cmd/devdraw/mkwsysrules.sh
+++ b/src/cmd/devdraw/mkwsysrules.sh
@@ -21,7 +21,9 @@
 fi
 
 if [ "x$WSYSTYPE" = "x" ]; then
-	if [ -d "$X11" ]; then
+	if [ "x`uname`" = "xDarwin" ]; then
+		WSYSTYPE=osx
+	elif [ -d "$X11" ]; then
 		WSYSTYPE=x11
 	else
 		WSYSTYPE=nowsys