Re-enable some coverage tests on Linux

[Zalathar]

These tests were originally disabled (on all platforms) in #110393, because those changes had made them start failing on Linux for unclear reasons.

I tried to re-enable them unconditionally in #111179, since they worked locally on my Mac, but I found that they were still failing on Linux, so I gave up at that time.

Later while working on #112300 I was able to re-enable them on Windows and Mac, since those changes made it possible to add specific ignore- directives to individual tests. I noticed at the time that the tests actually seemed to be working again on Linux, but by that point I didn't want to risk more CI failures, so I left them disabled on Linux with an intention to re-enable them later.

Now I'm going back to re-enable them on Linux too, since they seem to work fine.

---

Because run-coverage tests are sensitive to line numbers, and x test tidy doesn't like leading blank lines, I've replaced the old comment/ignore with an informative comment that occupies the same number of lines.

[rustbot]

r? @Mark-Simulacrum

(rustbot has picked a reviewer for you, use r? to override)

[Zalathar]

@rustbot label +A-code-coverage

[Zalathar]

From what I can tell, #110393 (comment) is referring to disabling these tests temporarily, in the hopes that future const changes would make them work again. So that seems to be the most likely explanation of why they're magically working again (though it's still a mystery why they broke in the first place).

[Zalathar]

(I'm using #112514 to verify that these tests will indeed work on Linux, since the x86_64-gnu-llvm-14 job that normally runs on PRs doesn't run the coverage tests.)

→ success https://github.com/rust-lang/rust/actions/runs/5470324669/jobs/9960279192

[Mark-Simulacrum]

@bors r+ rollup=iffy

[bors]

📌 Commit e4b81f6 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit e4b81f6 with merge 70d7283...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 70d7283 to master...

[rust-timer]

Finished benchmarking commit (70d7283): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.6%	[4.6%, 4.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.0%	[1.0%, 1.0%]	1
Regressions ❌ (secondary)	2.6%	[2.6%, 2.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.0%	[1.0%, 1.0%]	1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.4%	[3.2%, 3.6%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 659.399s -> 658.067s (-0.20%)