Tracking Issue: List of Nightly features

The following is rough list of nightly features used in Redox OS relibc crate.

• alloc_error_handler
  • possible stable workaround
• allocator_api
  • no stable workaround
• array_chunks
  • closed as "not planned"
  • easily refactored
• asm_const
  • stabilized with rustc upgrade
  • tracking issue closed: https://github.com/rust-lang/rust/issues/93332
• c_variadic
  • no stable workaround
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/44930
• core_intrinsics
  • only used for the low-level core::intrinsics::abort function to abort without unwinding
  • might be possible workarounds using platform-specific asm
• int_roundings
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/88581
  • can be removed (not used in the relibc codebase)
• maybe_uninit_slice
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/63569
  • only one use of MaybeUninit::assume_init_ref: <src/header/unistd/mod.rs:1164>
• lang_items
  • only needed for eh_personality
  • can potentially be refactored into a separate crate to provide the rust_eh_personality function
• let_chains
  • finalized stabilization work: https://github.com/rust-lang/rust/issues/53667
  • can be removed with upgrade to Rust v1.88.0 + edition 2024
• linkage
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/29603
  • used to provide weak linkage for a number of functions
  • potentially refactorable using global asm
• naked_functions
  • finalized stabilization work: https://github.com/rust-lang/rust/issues/32408
  • can be removed with Rust MSRV bump + edition 2024
  • appears to be unused?
• pointer_is_aligned_to
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/96284
  • can likely be refactored to replace the sanity check on the array length: <src/header/string/mod.rs:149-150>
• ptr_as_uninit
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/75402
  • potentially refactorable
• slice_as_chunks
  • tracking issue closed as not planned
  • refactorable using iterators
• stmt_expr_attributes
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/15701
  • only used in a single location in redox builds
  • potentially refactorable
• str_internals
  • not intended for general use
  • should be refactored if possible
  • appears to be unused?
• strict_provenance
  • finalized stabilization work: https://github.com/rust-lang/rust/issues/95228
  • can be removed with Rust MSRV bump + edition 2024
• sync_unsafe_cell
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/95439
  • unlikely to be refactored without a lot of work
• thread_local
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/29594
  • unlikely to be refactored without a lot of work
• vec_into_raw_parts
  • ongoing stabilization work: https://github.com/rust-lang/rust/issues/65816
  • unlikely to be refactored without a lot of work