Run standard library unit tests without optimizations in nopt CI jobs

[ecstatic-morse]

This was discussed in #73288 as a way to catch similar issues in the future. This builds an unoptimized standard library with the bootstrap compiler and runs the unit tests. This takes about 2 minutes on my laptop.

I confirmed that this method works locally, although there may be a better way of implementing it. It would be better to use the stage 2 compiler instead of the bootstrap one.

Notably, there are currently four libstd unit tests that fail in debug mode on i686-unkown-linux-gnu (a tier one target):

failures:
    f32::tests::test_float_bits_conv
    f32::tests::test_total_cmp
    f64::tests::test_float_bits_conv
    f64::tests::test_total_cmp

These are the tests that prompted #73288 as well as the ones added in #72568, which is currently broken due to #73328.

[Mark-Simulacrum]

I would rather add a dedicated flag (or perhaps third value for disable-optimize-tests) which builds std unoptimized and tests that; I suspect that should mostly be a matter of adjusting this to gate on rust_optimize_tests if we're and not pass --release if the cmd is "test". (We still want to build a release std).

We'll want to test, but I believe that should just work then on the nopt builders and get us the behavior we want (stage 2 testing).

[Mark-Simulacrum]

Actually to start off we may want some compiler team survey or so -- maybe there's no need for a separate flag, we can just integrate it directly. I would be fine with that personally but maybe there's value for "compiler" and "std"/test/etc tests being separated out.

[Mark-Simulacrum]

I'm going to relabel as waiting-on-author. I'll leave it up to you if you want to bring this up at a meeting (nominating it, I guess) to determine whether a dedicated flag or not makes sense, or instead implement separate flag(s).

[bors]

☔ The latest upstream changes (presumably #73650) made this pull request unmergeable. Please resolve the merge conflicts.

[Muirrum]

@ecstatic-morse This is a triage bump

[crlf0710]

Still needs a rebase...

[Mark-Simulacrum]

@bors try

[bors]

⌛ Trying commit b190d29cb370185f56da1952c20422c217d3b2cb with merge b527eeff23cea94181bdef3d291105be5addd1df...

[bors]

☀️ Try build successful - checks-actions, checks-azure
Build commit: b527eeff23cea94181bdef3d291105be5addd1df (b527eeff23cea94181bdef3d291105be5addd1df)

[Mark-Simulacrum]

@bors r+

Okay, I've rebased this and the try build came back successfully, so approving.

Looking back at what I said earlier, I think a dedicated option for "I want to run tests against no-opt versions of std" or so may make sense, but it need not block the minimal version here which doesn't require any bootstrap changes. This PR also gets us stage 0, i.e., cfg(bootstrap) testing of std, which is also a positive.

[bors]

📌 Commit 662871f has been approved by Mark-Simulacrum

[bors]

⌛ Testing commit 662871f with merge 43bec40...

[bors]

☀️ Test successful - checks-actions, checks-azure
Approved by: Mark-Simulacrum
Pushing 43bec40 to master...