just is a command runner, like make.
Simply install just, and copy the justfile into your source directory.
It can be named justfile or .justfile (to be "hidden") and can be added to .git/info/exclude so that git ignores it.
List commands with just (or just --list).
Add your own commands or contribute them back upstream here. See the manual for syntax and features.
Make sure to install the completions for your shell!
Set your build command using the $MAKE_CMD environment variable.
I use export MAKE_CMD="bear -- make" so that a compile_commands.json is generated when compiling, which can then be used by clangd.