How do you make osquery installer package for mac/ linux from source code, I mean the installer for installation and not the build process one.

Can you elaborate more on this? The release process we are following can be fully replicated locally (except for our signing process of course) We have the package data archive and unsigned packages created by osquery/osquery. This is mostly to support nightly testing. This package data is then passed to the osquery/osquery-packaging repository, which is responsible for taking the package data (contains binaries + control data used by various packaging formats, such as DEB, or MSI) and creating the final package

I was looking forward to get a package for macon my own instead of downloading it from osquery.io

yes, you can build your own package for macOS that way