SIGILL trying to build `bstr` in a no_std environment

Code

there is a bare-bone example in this repo
clone it then do
cargo build --target x86_64-unknown-none

Meta

rustc --version --verbose:

c 1.81.0 (eeb90cda1 2024-09-04)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: x86_64-unknown-linux-gnu
release: 1.81.0
LLVM version: 18.1.7

same problem for latest nightly as of writing this (nightly-2025-02-16) and beta too

Error output

error: could not compile `bstr` (lib)

Caused by:
  process didn't exit successfully: `/home/aler/.rustup/toolchains/nightly-2025-02-16-x86_64-unknown-linux-gnu/bin/rustc --crate-name bstr --edition=2021 /home/aler/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bstr-1.11.3/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=182 --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debuginfo=2 --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("alloc", "default", "serde", "std", "unicode"))' -C metadata=88315fca68f793d3 -C extra-filename=-838f38bd3ea009ac --out-dir /home/aler/Documents/head/target/x86_64-unknown-none/debug/deps --target x86_64-unknown-none -L dependency=/home/aler/Documents/head/target/x86_64-unknown-none/debug/deps -L dependency=/home/aler/Documents/head/target/debug/deps --extern memchr=/home/aler/Documents/head/target/x86_64-unknown-none/debug/deps/libmemchr-e902a720dd10a02a.rmeta --cap-lints allow -C panic=abort -C relocation-model=static` (signal: 4, SIGILL: illegal instruction)

i have also tried reporting this at bstr's repo

Clone the linked SafaOS/BStrFailsToCompile repository and first run cargo build --target x86_64-unknown-none with the reported toolchain versions. Compare the stable, beta, and nightly results while investigating the rustc compilation of bstr; done means the reproducible build no longer terminates with SIGILL.