nbd: fix gnutls dependency

Get rid of gnutls dependency introduced in 5bca84b. Needs patching
configure script to make gnutls existence test optional.

Signed-off-by: Marcin Jurkowski <marcin1j@gmail.com>

net/nbd/Makefile

@@ -51,7 +51,8 @@ define Package/nbd-server/description
 endef
 
 CONFIGURE_ARGS += \
-	--disable-glibtest
+	--disable-glibtest \
+	--without-gnutls
 
 TARGET_CFLAGS += --std=gnu99 -DNODAEMON
 

net/nbd/patches/100-make-gnutls-test-optional.patch

@@ -0,0 +1,15 @@
+--- a/configure.ac
++++ b/configure.ac
+@@ -210,7 +210,11 @@ dnl 		;;
+ dnl 	esac
+ dnl fi
+ 
+-PKG_CHECK_MODULES(GnuTLS, [gnutls >= 2.12.0],[HAVE_GNUTLS=1],[HAVE_GNUTLS=0])
++AC_ARG_WITH([gnutls], AS_HELP_STRING([--with-gnutls], [Build with GnuTLS]))
++AS_IF([test "x$with_gnutls" = "xyes"], [
++	PKG_CHECK_MODULES(GnuTLS, [gnutls >= 2.12.0],[HAVE_GNUTLS=1],[HAVE_GNUTLS=0])
++])
++
+ if test x$HAVE_GNUTLS = x1; then
+ 	AC_DEFINE(HAVE_GNUTLS, 1, [Define to 1 if you have a GnuTLS version of 2.12 or above])
+ else