Undefined reference to `getauxval` in function `init_have_lse_atomics` when compiling to nightly `aarch64-unknown-linux-musl`

[XAMPPRocky]

Code

I received this pull request, which caught a regression for aarch64-unknown-linux-musl when compiling for nightly. The same process works for stable and beta. I don't have a machine that can easily compile to this platform, so I can't reduce it at the moment: librasn/rasn#49

Version it worked on

It most recently worked on: Works on stable and beta 1.56.0-beta.4 (e6e620e1c 2021-10-04)

• https://github.com/XAMPPRocky/rasn/pull/49/checks?check_run_id=3827011175

Version with regression

rustc --version --verbose: 1.57.0-nightly (0eabf25 2021-10-06)

• https://github.com/XAMPPRocky/rasn/pull/49/checks?check_run_id=3827012571

Backtrace

= note: /rust/lib/rustlib/aarch64-unknown-linux-musl/lib/libcompiler_builtins-cbf6a032efba8222.rlib(cpu_model.o): In function `init_have_lse_atomics':
          /cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.49/./lib/builtins/cpu_model.c:786: undefined reference to `getauxval'
          collect2: error: ld returned 1 exit status
          
= help: some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
= note: use the `-l` flag to specify native libraries to link
= note: use the `cargo:rustc-link-lib` directive to specify the native libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)

[nbdd0121]

The reference is introduced in llvm/llvm-project@a4ac434#diff-a380831627112e2516d39595d94e711db7ac63316b9c411aa77af4a561d15ab8

[nbdd0121]

@rustbot label E-needs-bisection

[XAMPPRocky]

Tagging #76992 and #85805 since they seem relevant and maybe a potential fix.

[apiraino]

forcing notification for prioritization

@rustbot label -I-prioritize +T-compiler +I-prioritize