spurious? failure in test-float-parse

https://triage.rust-lang.org/gha-logs/rust-lang/rust/72001231929

This is on the aarch64-apple runner.

Skipping test 'f16 large positive exponents'
Skipping test 'f16 random digits'
Skipping test 'f16 small exponents'
Skipping test 'f32 exhaustive'
Skipping test 'f32 large positive exponents'
Skipping test 'f32 random digits'
Skipping test 'f32 small exponents'
Skipping test 'f64 fuzz'
Skipping test 'f64 large positive exponents'
Skipping test 'f64 random digits'
Skipping test 'f64 small exponents'
Launching all
Launching test 'f16 subnormal edge cases'
Launching test 'f32 subnormal edge cases'
Launching test 'f64 subnormal edge cases'
Launching test 'f16 regression check'
Launching test 'f32 regression check'
Launching test 'f64 regression check'
Launching test 'f16 special values'
Launching test 'f32 special values'
Launching test 'f64 special values'
Launching test 'f16 fuzz'
Launching test 'f16 subnormal'
Launching test 'f16 few ones float'
Launching test 'f16 few ones int'
Launching test 'f16 repeating decimal'
Launching test 'f32 repeating decimal'
Launching test 'f64 repeating decimal'
Launching test 'f32 few ones float'
Launching test 'f32 few ones int'
Launching test 'f16 large integer values'
Launching test 'f32 large integer values'
Launching test 'f64 large integer values'
Launching test 'f32 fuzz'
Launching test 'f16 exhaustive'
Launching test 'f64 few ones int'
Launching test 'f64 few ones float'
Launching test 'f16 small integer values'
Launching test 'f32 small integer values'
Launching test 'f64 small integer values'
Launching test 'f32 subnormal'
Launching test 'f64 subnormal'
[ a bunch of blank lines ]
thread '<unnamed>' (2004930) panicked at /Users/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/num-bigint-0.4.6/src/biguint.rs:89:5:
assertion failed: b.last() != Some(&0)
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: num_bigint::biguint::division::div_rem_ref
   4: <num_bigint::bigint::BigInt as num_integer::Integer>::div_rem
   5: <num_bigint::bigint::BigInt as core::ops::arith::Div>::div
   6: <num_rational::Ratio<num_bigint::bigint::BigInt> as core::ops::arith::Sub>::sub
   7: test_float_parse::validate::validate::<f32>
   8: <&rayon::iter::par_bridge::IterParallelProducer<test_float_parse::gen_::subnorm::SubnormComplete<f32>> as rayon::iter::plumbing::UnindexedProducer>::fold_with::<rayon::iter::map_with::MapWithFolder<rayon::iter::try_reduce::TryReduceFolder<rayon::iter::ParallelIterator::try_for_each_init::ok<core::result::Result<(), test_float_parse::EarlyExit>>, core::result::Result<(), test_float_parse::EarlyExit>>, alloc::string::String, test_float_parse::test_runner<f32, test_float_parse::gen_::subnorm::SubnormComplete<f32>>::{closure#0}>>
   9: rayon::iter::plumbing::bridge_unindexed_producer_consumer::<&rayon::iter::par_bridge::IterParallelProducer<test_float_parse::gen_::subnorm::SubnormComplete<f32>>, rayon::iter::map_with::MapInitConsumer<rayon::iter::try_reduce::TryReduceConsumer<rayon::iter::ParallelIterator::try_for_each_init::ok<core::result::Result<(), test_float_parse::EarlyExit>>, <() as core::default::Default>::default>, <alloc::string::String>::new, test_float_parse::test_runner<f32, test_float_parse::gen_::subnorm::SubnormComplete<f32>>::{closure#0}>>
  10: <rayon_core::job::StackJob<rayon_core::latch::SpinLatch, rayon_core::join::join_context::call_b<core::result::Result<(), test_float_parse::EarlyExit>, rayon::iter::plumbing::bridge_unindexed_producer_consumer<&rayon::iter::par_bridge::IterParallelProducer<test_float_parse::gen_::subnorm::SubnormComplete<f32>>, rayon::iter::map_with::MapInitConsumer<rayon::iter::try_reduce::TryReduceConsumer<rayon::iter::ParallelIterator::try_for_each_init::ok<core::result::Result<(), test_float_parse::EarlyExit>>, <() as core::default::Default>::default>, <alloc::string::String>::new, test_float_parse::test_runner<f32, test_float_parse::gen_::subnorm::SubnormComplete<f32>>::{closure#0}>>::{closure#1}>::{closure#0}, core::result::Result<(), test_float_parse::EarlyExit>> as rayon_core::job::Job>::execute
  11: <rayon_core::registry::WorkerThread>::wait_until_cold
  12: <rayon_core::registry::ThreadBuilder>::run
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
Command `/Users/runner/work/rust/rust/build/aarch64-apple-darwin/stage0/bin/cargo run -Zwarnings --target aarch64-apple-darwin -Zbinary-dep-depinfo -j 3 -Zroot-dir=/Users/runner/work/rust/rust --locked --color=always --profile=release --manifest-path /Users/runner/work/rust/rust/src/tools/test-float-parse/Cargo.toml -- --skip-huge [workdir=/Users/runner/work/rust/rust]` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:191:21
Executed at: src/bootstrap/src/core/build_steps/test.rs:4203:30

Start by reproducing the aarch64-apple failure with the cargo command shown in the report, then inspect src/tools/test-float-parse around the validate path and subnormal generator named in the backtrace. Check the bootstrap call sites in src/bootstrap/src/core/build_steps/tool.rs and test.rs for context. Done means determining the cause and making the test command complete without the num-bigint panic.