lesstif: needs MMU

Fixes:
http://autobuild.buildroot.net/results/9f7/9f718c9c9907d9aa2a7a0c45c872f5a8f34b8399/

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/lesstif/Config.in

@@ -4,6 +4,7 @@ config BR2_PACKAGE_LESSTIF
 	select BR2_PACKAGE_XLIB_LIBXT
 	select BR2_PACKAGE_XLIB_LIBXEXT
 	select BR2_PACKAGE_FREETYPE
+	depends on BR2_USE_MMU # fork()
 	help
 	  lesstif is the Hungry Programmers' version of OSF/Motif