Missing user_fpxregs_struct on musl x86

[ptrcnull]

user_fpxregs_struct does exist in musl, but doesn't seem to be available in the libc crate:

10:34.49 error[E0432]: unresolved import `libc::user_fpxregs_struct`
10:34.49  --> /builds/alpine/aports/community/firefox/src/firefox-120.0.1/third_party/rust/minidump-writer/src/linux/thread_info/x86.rs:5:5
10:34.49   |
10:34.49 5 | use libc::user_fpxregs_struct;
10:34.49   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ no `user_fpxregs_struct` in the root
10:34.52 error[E0432]: unresolved imports `libc::user`, `libc::user_fpregs_struct`, `libc::user_regs_struct`
10:34.52  --> /builds/alpine/aports/community/firefox/src/firefox-120.0.1/third_party/rust/minidump-writer/src/linux/thread_info/x86.rs:7:12
10:34.52   |
10:34.52 7 | use libc::{user, user_fpregs_struct, user_regs_struct};
10:34.52   |            ^^^^  ^^^^^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^^ no `user_regs_struct` in the root
10:34.52   |            |     |
10:34.52   |            |     no `user_fpregs_struct` in the root
10:34.52   |            no `user` in the root
10:34.55 error[E0412]: cannot find type `_libc_fpreg` in crate `libc`
10:34.55   --> /builds/alpine/aports/community/firefox/src/firefox-120.0.1/third_party/rust/minidump-writer/src/linux/crash_context/x86.rs:53:71
10:34.55    |
10:34.55 53 |             debug_assert_eq!(fs._st.len() * std::mem::size_of::<libc::_libc_fpreg>(), 80);
10:34.55    |                                                                       ^^^^^^^^^^^ not found in `libc`
10:34.55 error[E0412]: cannot find type `_libc_fpreg` in crate `libc`
10:34.55   --> /builds/alpine/aports/community/firefox/src/firefox-120.0.1/third_party/rust/minidump-writer/src/linux/crash_context/x86.rs:57:62
10:34.55    |
10:34.55 57 |                     fs._st.len() * std::mem::size_of::<libc::_libc_fpreg>(),
10:34.55    |                                                              ^^^^^^^^^^^ not found in `libc`

[ptrcnull]

it's been pointed out to me that it's not just fpxregs, but also user_fpregs_struct user_regs_struct and _libc_fpreg; the two former available in musl in the same file, but the latter doesn't seem to exist under the same name