dialog: needs mmu

Fixes
http://autobuild.buildroot.net/results/bfb968d611e8dea43c604726a3005c72a7d6ee28/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/dialog/Config.in

@@ -1,6 +1,7 @@
 config BR2_PACKAGE_DIALOG
 	bool "dialog"
 	depends on BR2_TOOLCHAIN_HAS_THREADS # fork()
+	depends on BR2_USE_MMU # fork()
 	select BR2_PACKAGE_NCURSES
 	select BR2_PACKAGE_LIBICONV if !BR2_ENABLE_LOCALE
 	help