directfb: don't build tools for target

Normally these aren't needed, and some of them (mkdgifft) needs C++
support.

Alternatively we could add an option (depending on HAVE_DEVFILES) to
build these.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/directfb/directfb.mk

@@ -26,7 +26,8 @@ DIRECTFB_CONF_OPT = \
 	--disable-vnc \
 	--disable-osx \
 	--disable-video4linux \
-	--disable-video4linux2
+	--disable-video4linux2 \
+	--without-tools
 
 DIRECTFB_DEPENDENCIES = freetype zlib