Describe the feature or problem you’d like to solve

1. when building in containers (e.g distrobox), to use installed software, you need to install it into mounted volumes like ~/.local/share, because system-wide directories cannot be accessed from host system.
2. however, github cli is installed to hardcoded /usr/local path, making this hard.

Proposed solution

the install prefix in the Makefile should be configurable. for example, prefix=~/.local/share make install.

Additional context

this would make installing the GitHub CLI much easier in restricted or non-standard environments.