quagga: depends on MMU

Fixes:

  http://autobuild.buildroot.org/results/1c5/1c5fdfe3a0248b65efdea0594d8367ff907015d4/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/quagga/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_QUAGGA
 	bool "quagga"
+	depends on BR2_USE_MMU # fork()
 	help
 	  Routing software suite, providing implementations of
 	  OSPFv2, OSPFv3 (IPv6), RIP v1 and v2, RIPng (IPv6) and BGPv4+.