compiletest: clarify COMPILETEST_NEEDS_ALL_LLVM_COMPONENTS error

[RalfJung]

COMPILETEST_NEEDS_ALL_LLVM_COMPONENTS is a confusing name because elsewhere "needs" means "ignore when requirement not met", but here it means "fail when requirement not met".

[rustbot]

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[rustbot]

Some changes occurred in src/tools/compiletest

cc @jieyouxu

[workingjubilee]

this is just some diagnostics/nomenclature changes to stuff we confirmed worked this way in #125702

@bors r+

[bors]

📌 Commit 4ce7e09 has been approved by workingjubilee

It is now in the queue for this repository.

[bors]

⌛ Testing commit 4ce7e09 with merge 434999e...

[bors]

☀️ Test successful - checks-actions
Approved by: workingjubilee
Pushing 434999e to master...

[rust-timer]

Finished benchmarking commit (434999e): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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Bootstrap: 670.547s -> 672.444s (0.28%)
Artifact size: 318.70 MiB -> 318.74 MiB (0.01%)