[3np]

> probably settle for automatic build system detection based on archive structure there

Please add knobs for the end user to manually configure this per package and global default before adding autodetection. As a user to is very frustrating to have to patch the package manager to override some well-intentioned automagic which didn't consider my setup or dig through sources to uncover some undocumented assumption. yarn is a cautionary example.

[alexykn]

I'll add manual override flags and also let users not only build from source from formulae but any dir on their machine they want, only makes sense