Use llvm-libunwind="in-tree" for Fuchsia targets

[andrewpollack]

With updates to Fuchsia CI's Zircon libraries #99833, we can introduce llvm-libunwind="in-tree" for Fuchsia targets. This PR restores functionality removed from #93604 (comment).

cc @tmandry@djkoloski

[rust-highfive]

r? @jyn514

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[tmandry]

Can you also update the target docs so they don't say you need to override this anymore?

[andrewpollack]

Can you also update the target docs so they don't say you need to override this anymore?

Good call -- done!

[tmandry]

The bootstrap changes were already approved in #93604 (comment).

@bors r+ rollup=never (broke last time)

[bors]

📌 Commit 29238f4 has been approved by tmandry

It is now in the queue for this repository.

[bors]

⌛ Testing commit 29238f4 with merge 24041dbeb7a469050367aa1d63309a708fc46af1...

[bors]

💥 Test timed out

[jyn514]

@bors retry

[bors]

⌛ Testing commit 29238f4 with merge e8dc8bc...

[bors]

☀️ Test successful - checks-actions
Approved by: tmandry
Pushing e8dc8bc to master...

[rust-timer]

Finished benchmarking commit (e8dc8bc): comparison url.

Instruction count

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: ✅ relevant improvement found

	mean1	max	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	-0.2%	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

• Primary benchmarks: mixed results
• Secondary benchmarks: ✅ relevant improvement found

	mean1	max	count2
Regressions ❌ (primary)	1.7%	2.3%	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.9%	-2.9%	1
Improvements ✅ (secondary)	-3.6%	-3.6%	1
All ❌✅ (primary)	0.5%	-2.9%	4

Cycles

Results

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

	mean1	max	count2
Regressions ❌ (primary)	3.1%	3.9%	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.0%	-3.0%	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.0%	3.9%	3

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↩³

2. number of relevant changes↩↩²↩³