openconnect: build without options we don't support

That is, since we don't require gssapi or libpskc, avoid
accidental builds with it.

Closes #5474

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>

net/openconnect/Makefile

@@ -53,6 +53,8 @@ CONFIGURE_ARGS += \
 	--with-vpnc-script=/lib/netifd/vpnc-script \
 	--without-libpcsclite \
 	--without-stoken \
+	--without-libpskc \
+	--without-gssapi \
 	--without-lz4
 
 ifeq ($(CONFIG_OPENCONNECT_OPENSSL),y)