Fix x build library/std compiler/rustc

[jyn514]

Previously, this was broken because of improper caching:

1. StepDescription::maybe_run builds Compile::Std, which only built std and not proc_macro
2. Std calls builder.ensure(StdLink)
3. Rustc calls ensure(Std), which builds all crates, including proc_macro
4. Rustc calls ensure(StdLink). ensure would see that it had already been run and do nothing. <-- bug is here
5. Cargo gives an error that proc_macro doesn't exist.

This fixes the caching by adding crates to StdLink, so it will get rerun if the crates that are built change.

Fixes #99129.

[rust-highfive]

r? @Mark-Simulacrum

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[Mark-Simulacrum]

RustcLink presumably needs the same treatment?

[jyn514]

ah, good call - not sure how you could trigger this for RustcLink, since it's only called from impl Step for Rustc, but it's good to future proof in case we want to build individual crates (e.g. for rustfmt) in the future.

[Mark-Simulacrum]

@bors r+ rollup p=5 (breaking builds for folks in practice)

[bors]

📌 Commit 7d4bd54 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[jyn514]

@Mark-Simulacrum I don't think https://rust-lang.zulipchat.com/#narrow/stream/247081-t-compiler.2Fperformance/topic/NIghtly.20bustage.3F is actually related - the problem there is that library/std means something different than it used to ("build std" instead of "build all crates in the standard library"). This only affects specifically build library/std compiler/rustc, not build library/std and then rustc +local ....

[Mark-Simulacrum]

Yes, I agree, but I think this is still something we should fix fairly quickly; maybe @bors p=1 though.

[bors]

⌛ Testing commit 7d4bd54 with merge a51fb2b...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing a51fb2b to master...

[rust-timer]

Finished benchmarking commit (a51fb2b): comparison url.

Instruction count

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: 🎉 relevant improvements found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-1.5%	-1.8%	6
All 😿🎉 (primary)	N/A	N/A	0

Max RSS (memory usage)

Results

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: mixed results

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	3.6%	3.6%	1
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-2.4%	-3.0%	3
All 😿🎉 (primary)	N/A	N/A	0

Cycles

This benchmark run did not return any relevant results for this metric.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

1. the arithmetic mean of the percent change ↩ ↩²

2. number of relevant changes ↩ ↩²