How to install packages without any package manager

I would like to install a package, let's say openssh-client, in my distribution. The problem is that none of the package managers I know are installed on it.

# sudo apt-get install openssh
sudo: apt-get: command not found
# ipkg update
-sh: ipkg: not found
# opkg
-sh: opkg: not found
# dpkg
-sh: dpkg: not found
# apt-get 
-sh: apt-get: not found

The distribution is a minimal one built using BuildRoot. During the system configuration, I specified the package managers I wanted to use but none of them were installed... How can I install a package or a package manager without any utility?