Cannot write tests that need the csky backend

[RalfJung]

In tests/ui/abi/compatibility.rs we're trying to test the ABI adjustment logic of all targets. This generally works as the test is no_core and LLVM has backends for all targets available -- except it does not seem possible to test the csky target that way. Trying to add the usual needs-llvm-components: csky leads to an error from tidy:

/checkout/tests/ui/abi/compatibility.rs: revision csky specifies unknown LLVM component `csky`

The test passes just fine locally, so it seems like at least the downloaded LLVM has the csky component. I don't know why it was not added to tidy's KNOWN_LLVM_COMPONENTS list.

Cc @Dirreke

[workingjubilee]

cc @erikdesjardins but also I think this was just an oversight.

[RalfJung]

FWIW if one just adds this to a test it does pass on CI

//@revisions: csky
//@[csky] compile-flags: --target csky-unknown-linux-gnuabiv2
//@[csky] needs-llvm-components: csky

but of course it may just be silently ignored, hard to say whether the test actually runs... this needs-llvm-components stuff makes tests quite fragile. :/

[workingjubilee]

Yeah, the tidy check was added to reduce the fragility because a lot of people were giving names other than the LLVM component's name, like riscv64 instead of riscv, etc.

[RalfJung]

The remaining question then is, how sure are we that the components accepted by tidy are all available on some CI runner?

[RalfJung]

Also, something else must have been going on... I disabled this test before that sanity check was added to tidy.

Sadly the logs for this failure are already gone.