"./sub: error while loading shared libraries: libmosquitto.so.1: cannot open shared object file: No such file or directory"

Assuming you have installed the libraries to /usr/local/lib, which is the default, the correct answer is to run /sbin/ldconfig as root/sudo.

On some systems you will need to add /usr/local/lib to the paths that ld caches, e.g.

echo /usr/local/lib > /etc/ld.so.conf.d/local.conf