libvncserver: disable on nios2, due to binutils issues

Fixes:

  http://autobuild.buildroot.org/results/469/469d5667f05ca6954805772fcaaa2b33dfdc6167/

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

package/libvncserver/Config.in

@@ -1,6 +1,8 @@
 config BR2_PACKAGE_LIBVNCSERVER
 	bool "libvncserver"
 	depends on BR2_USE_MMU # VNCommand.c uses fork()
+	# binutils issue (bad expression)
+	depends on !BR2_nios2
 	help
 	  libvncserver is a VNC server/client library.