compiletest: "ignore-debug" tests are ignored even with debug-assertions-std = false

[RalfJung]

Some tests need to be disabled when the standard library is built with debug assertions, since that can affect mir-opts codegen through inlining. For that purpose we have the ignore-debug clause in compiletest. However, unfortunately it seems like compiletest actually checks whether the compiler is built with debug assertions, even though that should not make any difference. I have

debug-assertions = true
debug-assertions-std = false

and these tests should not be ignored, but they are.

We should maybe rename the directive to ignore-debug-std to make it more clear what this is about.

[RalfJung]

This seems to be currently implemented here:

rust/src/tools/compiletest/src/header/cfg.rs

Lines 197 to 201 in 795ade0

	condition! {
	name: "debug",
	condition: cfg!(debug_assertions),
	message: "when building with debug assertions",
	}

so it really checks whether compiletest is built with debug assertions, which of course is not what tests actually care about. Though I guess one hacky way to resolve this then would be to build compiletest with debug assertions only if the standard library is built with debug assertions... but probably it would be better if bootstrap would set some sort of env var so that compiletest can know whether the standard library was built with debug assertions.