enabling instrumentation for stage 3 compilers

[nobellium1997]

This commit allows users to instrument their stage 3 compilers.

This PR is a revival of the following PR: #101744

The aim is to break up the PR into smaller chunks and merge these changes in piecemeal. The PR here is to allow us to instrument stage 3 rust compilers as stage 3 instrumentation is part of how we create profiles for guided optimization later on.

[rustbot]

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[Kobzol]

Hi, could you say more about the use-case please? (the change looks simple enough though)

[jieyouxu]

I'm curious to hear more on ^ as well, but the change itself seems reasonable indeed.

[nobellium1997]

许杰友 Jieyou Xu (Joe) ***@***.***> writes:

jieyouxu left a comment (rust-lang/rust#157930) I'm curious to hear more on ^ as well, but the change itself seems reasonable indeed. -- Reply to this email directly or view it on GitHub: #157930 (comment) You are receiving this because you authored the thread. Message ID: ***@***.***>

Hi sorry honestly I'm trying to figure out why we instrument the stage 3 compiler myself. Our optimization pipeline is quite complex so it's taking me a while to understand it. I think for now we can simply un-assign this PR while I try to understand things better.

[rust-bors]

☔ The latest upstream changes (presumably #159057) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.