alsamixergui: needs mmu

Because of the new fl_open_uri() function since the fltk bump using
fork().

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/alsamixergui/Config.in

@@ -1,6 +1,7 @@
 config BR2_PACKAGE_ALSAMIXERGUI
 	depends on BR2_PACKAGE_XORG7
 	depends on BR2_INSTALL_LIBSTDCPP
+	depends on BR2_USE_MMU # fltk fork()
 	select BR2_PACKAGE_FLTK
 	select BR2_PACKAGE_ALSA_LIB
 	select BR2_PACKAGE_ALSA_LIB_PCM