$ sudo apt-get update
$ sudo apt-get install librpmbuild3 

librpmbuild3 is installed in your system.

Make ensure the librpmbuild3 package were installed using the commands given below,

$ sudo dpkg-query -l | grep librpmbuild3 *

You will get with librpmbuild3 package name, version, architecture and description in a table

librpmbuild3 package basic information: