fix(test): skip dwp uplift test without packed debuginfo

[HNO3Miracle]

What does this PR try to resolve?

Fix: rust-lang/rust#158213.

uplift_dwp_of_bin_on_linux assumes all Linux hosts can produce .dwp files by requesting -Csplit-debuginfo=packed. That is not true for every Linux target. For example, riscv64gc-unknown-linux-gnu currently reports only off from rustc --print=split-debuginfo.

When Cargo sees that packed is unsupported, it correctly avoids passing -Csplit-debuginfo=packed, so rustc does not emit .dwp files. The test then fails because it still unconditionally expects those files.

This PR adds a requires_host_split_debuginfo = "packed" option to the cargo_test macro and uses it for the .dwp uplift test, so unsupported hosts show the test as ignored instead of silently returning.

How to test and review this PR?

The main behavior to review is that the test still runs on Linux hosts that support packed, while being marked ignored on Linux hosts like RISC-V where Cargo cannot request packed split debuginfo.

Tested with:

build/x86_64-unknown-linux-gnu/rustfmt/bin/rustfmt --check src/tools/cargo/crates/cargo-test-macro/src/lib.rs src/tools/cargo/tests/testsuite/build.rs
RUST_BACKTRACE=1 ./x test --stage 2 src/tools/cargo --test-args "build::uplift_dwp_of_bin_on_linux --exact --nocapture"

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Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: @ehuss, @epage, @weihanglo
• @ehuss, @epage, @weihanglo expanded to ehuss, epage, weihanglo
• Random selection from ehuss, epage, weihanglo

[ehuss]

Tests that silently don't do anything can be difficult to debug or notice if they aren't working correctly. Usually we try to add the ignore attribute when possible to make it visible. Would it be possible to instead add a requires_host_split_debuginfo = "packed" to the cargo_test macro? I think it shouldn't require too many extra lines of code. There are several examples there which call the set_ignore! macro, and I think the code you have in rustc_supports_split_debuginfo would essentially be the same, just moved over there.

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[HNO3Miracle]

That really makes sense! And I will revise it.

Thanks for the review!

[HNO3Miracle]

And I'm wondering if current diff is proper. Wishing for further opinion!

[ehuss]

Thanks!

If the macro grows more over time, we might consider adding more helper functions to reduce some of the duplication, but I don't think it is necessarily urgent right now.

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