cmd/builder: decide what to do w/ `dist_`

[codeboten]

In #13304, a discussion about whether or not dist_ replacements should be supported and documented, or removed altogether was started. I'm opening this issue to come up with a decision one way or the other about it.

I would propose removing support for this as it is not currently documented, but I'm likely missing some historical context here.

My understanding is that the purpose of the replace was to allow people to set (eg.) the DIST_OUTPUT_PATH environment variable in order to set the dist::output_path config. Adding dots in environment variable names is difficult, but splitting on underscores would have prevented specifying "output_path". It's a bit of a hacky solution though...

But as you said, setting config through environment variables isn't documented anywhere, and it's not clear who if anyone is using this, so maybe it would be worth it either removing this hacky partial support, or adding more proper support for it.

Originally posted by @jade-guiton-dd in #13304 (comment)

[mx-psi]

I would rather remove support for this if there is no clear signal that our users are using it