Fix CI on FreeBSD 13 i686

[neuschaefer]

Description

Investigating why there's a test failure on FreeBSD 13 i686

• FreeBSD 13.5 doesn't resolve the issue
• FreeBSD 13.3 reportedly seems more stable, but isn't available anymore (image download fails with 404)

Sources

TODO

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

[tgross35]

I don't have a link handy but IIRC there were some issues segfaults on FreeBSD13 (maybe in the Cargo repo?). @asomers would know more

[asomers]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=285873 is the bug for the cargo segfaults on FreeBSD 13. It's still unsolved.

[tgross35]

Rebase after #4648 once that lands, since it changes the ctest implementation, might happen to fix things (though unlikely...)

[tgross35]

...oh, or it may make things worse. Does the toolchain not support that way of getting the size of a field without reading uninit data?

cargo:warning=/tmp/cirrus-ci-build/target/i686-unknown-freebsd/debug/build/libc-test-656b2cab6c3a5f55/out/ctest_output.c:37608:20: error: variable has incomplete type 'struct reg32'
  cargo:warning= 37608 |     return sizeof(((struct reg32){}).r_edi);