glossary: add entry for rustbuild

[lolbinarycat]

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[rustbot]

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[Noratrieb]

I see it more as the old name, I'd call the rust part bootstrap too

[lolbinarycat]

Yes, I would say bootstrap is the whole system of bootstrap.py + rustbuild.

The name "rustbuild" still gets used a fair bit by t-bootstrap when the distinction between the two parts is meaningful. I honestly had no idea the history of the name, I just noticed it was a term people were using that didn't seem to be written down anywhere really.

[jieyouxu]

I don't think this is actually used that way? At least, I don't use rustbuild to refer to the rust part, I call that bootstrap, and disambiguate from the python part by calling the python part bootstrap.py or "the python wrapper" etc. etc.

[Noratrieb]

rust-lang/rust#127434