czmq: disable nss

While bumping czmq to version 4.2.1 from master branch into OpenWrt
19.07, it automatically detects nss when compiled before czmq.

These steps can verify this:

make package/nss/compile V=s
make package/czmq/compile V=s

Then czmq requires many dependencies:
Package czmq is missing dependencies for the following libraries:
libnspr4.so
libnss3.so
libnssutil3.so
libplc4.so
libplds4.so
libsmime3.so
libsoftokn3.so
libssl3.so

And this fails. If you are using SDK and wants to have just a few
packages then czmq gets compiled if any of those packages are not
present in build system.

This was also mentioned in the release notes for czmq 4.2.1:
https://github.com/zeromq/czmq/releases/tag/v4.2.1

> Note for packagers: NSS can now be used and linked against to avoid using
an internal embedded reimplementation of SHA. It is enabled by default if
present.

NSS was disabled before, so let's disable it.

This is required only for OpenWrt 19.07 as this is done differently in OpenWrt 21.02 and OpenWrt
master and czmq is compiled there.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>

libs/czmq/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=czmq
 PKG_VERSION:=4.2.1
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://github.com/zeromq/czmq/releases/download/v$(PKG_VERSION)/
@@ -42,7 +42,7 @@ define Package/czmq/description
 endef
 
 TARGET_CFLAGS += --std=c99
-CONFIGURE_ARGS += --without-docs
+CONFIGURE_ARGS += --without-docs --with-nss=no
 
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/lib/pkgconfig