Cannot find mosquitto dev files for Onion Omega

I am using an Onion Omega 2+(runs on OpenWRT OS) for a project and want to compile a C/C++ source code. To do that, I have installed GCC using an external SD card because of the memory limitation. I followed this link to do that. One of my project's requirements is to use mosquitto broker locally. I've been facing issues getting the mosquitto dev package to use the required headers and library file for the code to compile. Is there a way to install mosquito to get the required files?

You can't compile on your device, OpenWrt is not self-hosting and there are no installable -dev packages. If you need to compile something, you need to use the SDK or buildroot and cross-compile it (and prior everything it depends on).