test failures with Rust 1.75+ when running in `--release` mode

[decathorpe]

We're running the half crate's tests during our package builds in Fedora Linux and our CI has detected that since the update to Rust 1.75.0, some tests have started to fail - but only when run in --release mode:

failures:
---- bfloat::test::test_nan_conversion_to_larger stdout ----
thread 'bfloat::test::test_nan_conversion_to_larger' panicked at src/bfloat.rs:1531:9:
assertion failed: neg_nan64_from_32.is_nan() && neg_nan64_from_32.is_sign_negative()
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
---- bfloat::test::test_nan_conversion_to_smaller stdout ----
thread 'bfloat::test::test_nan_conversion_to_smaller' panicked at src/bfloat.rs:1502:9:
assertion failed: neg_nan32_from_64.is_nan() && neg_nan32_from_64.is_sign_negative()
---- binary16::test::test_nan_conversion_to_larger stdout ----
thread 'binary16::test::test_nan_conversion_to_larger' panicked at src/binary16.rs:1599:9:
assertion failed: neg_nan64_from_32.is_nan() && neg_nan64_from_32.is_sign_negative()
---- binary16::test::test_nan_conversion_to_smaller stdout ----
thread 'binary16::test::test_nan_conversion_to_smaller' panicked at src/binary16.rs:1570:9:
assertion failed: neg_nan32_from_64.is_nan() && neg_nan32_from_64.is_sign_negative()
failures:
    bfloat::test::test_nan_conversion_to_larger
    bfloat::test::test_nan_conversion_to_smaller
    binary16::test::test_nan_conversion_to_larger
    binary16::test::test_nan_conversion_to_smaller