`trailing_field_offset!` test failing on nightly-2024-05-30

[joshlf]

#1364 rolls our pinned nightly from 2024-05-29 to 2024-05-30, resulting in these CI failures:

• (zerocopy / nightly / --all-features / i686-unknown-linux-gnu)
• (zerocopy / nightly / --features __internal_use_only_features_that_work_on_stable / x86_64-unknown-linux-gnu)
• (zerocopy / nightly / --all-features / x86_64-unknown-linux-gnu)

In #1366, which updates the v0.7.x branch, there are many more CI failures, all with the same error.

Curiously, only the second CI job produces output from the failing test, while the other two fail silently:

thread 'macro_util::tests::test_trailing_field_offset' panicked at src/macro_util.rs:604:9:
assertion `left == right` failed
  left: Some(0)
 right: Some(1)

This comes from:

zerocopy/src/macro_util.rs

Line 604 in e670efe

test!(#[repr(C)] #[repr(packed)] (u8; u8) => Some(1));

Based on the set of CI jobs which failed, based on the fact that #1366 has more failures, and based on the fact that I was unable to reproduce locally on a 64-bit Apple M3, I suspect this failure may be nondeterministic, but I'm not positive.