ci: Test powerpc64-unknown-linux-musl in tier 2

[Gelbpunkt]

Description

Since 1.95.0, this is now a tier 2 target.

Sources

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

[Gelbpunkt]

This is going to be a bit of fun, since the Ubuntu cross compilation toolchain is for ELFv1. We'll have to compile libgcc ourselves or just start using the Rust CI images that contain ready-to-use toolchains.

[tgross35]

Could you say a bit more about where the mismatch comes from? I'm not sure why -musl hits the issue but -gnu isn't.

Using a prebuilt toolchain specifically for this target sounds nicer if possible, as long setup isn't too crazy.

[Gelbpunkt]

Could you say a bit more about where the mismatch comes from? I'm not sure why -musl hits the issue but -gnu isn't.

The -musl target uses the ELFv2 ABI, while the -gnu target uses ELFv1. Ubuntu's toolchain can be forced to compile for ELFv2 with -mabi=elfv2, but the libgcc.a it bundles is for ELFv1 and cannot be linked together with ELFv2 objects.

Using a prebuilt toolchain specifically for this target sounds nicer if possible, as long setup isn't too crazy.

Rustup does this, they have a shell script to fetch the Docker base images from the r-l/r CI and use that for getting a ready to use toolchain.