compiletest: Support forbid-output in UI tests

[clubby789]

The forbid-output directive is currently only run in incremental tests (although no incremental tests use it). There are some UI tests 'using' it, but it's doing nothing 😄 Let's fix this

Will also PR the dev guide to note this.

dev-guide PR: rust-lang/rustc-dev-guide#2171

[rustbot]

r? @albertlarsan68

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[rustbot]

Some changes occurred in src/tools/compiletest

cc @jieyouxu

[jieyouxu]

Wait, so this is like the dual of error-pattern. Can we rename this to forbid-error-pattern maybe?

[jieyouxu]

Actually, I'll revisit forbid-output in a follow-up because the naming is strange and inconsistent versus error-pattern and normalize-stderr-test and whatever...

[jieyouxu]

@bors r+ rollup=iffy (who knows if any tests actually should've failed but never did)

[bors]

📌 Commit 5a8ecc9 has been approved by jieyouxu

It is now in the queue for this repository.

[bors]

⌛ Testing commit 5a8ecc9 with merge a0a5c42...

[bors]

☀️ Test successful - checks-actions
Approved by: jieyouxu
Pushing a0a5c42 to master...

[rust-timer]

Finished benchmarking commit (a0a5c42): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

• If the regression was expected or you think it can be justified,
  please write a comment with sufficient written justification, and add
  @rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
• If you think that you know of a way to resolve the regression, try to create
  a new PR with a fix for the regression.
• If you do not understand the regression or you think that it is just noise,
  you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
  were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.4%	[0.4%, 0.4%]	1
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.1%]	2
Improvements ✅ (secondary)	-0.3%	[-0.4%, -0.2%]	6
All ❌✅ (primary)	-0.2%	[-0.2%, -0.1%]	2

Max RSS (memory usage)

Results (primary -2.9%, secondary 2.5%)

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)	2.5%	[2.1%, 2.8%]	3
Improvements ✅ (primary)	-2.9%	[-2.9%, -2.9%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.9%	[-2.9%, -2.9%]	1

Cycles

Results (secondary 4.0%)

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)	4.0%	[2.4%, 5.5%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 763.93s -> 763.617s (-0.04%)
Artifact size: 330.53 MiB -> 330.57 MiB (0.01%)

[lqd]

Test only change. Gotta be noise.

@rustbot label: +perf-regression-triaged