erlang: needs mmu

Fixes:
http://autobuild.buildroot.net/results/5b3411008ddf89aef55c8dd8682b894cf9860d13/

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

package/erlang/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_ERLANG
 	bool "erlang"
+	depends on BR2_USE_MMU # fork()
 	help
 	  Erlang is a programming language used to build massively scalable
 	  soft real-time systems with requirements on high availability.