Remove more #[must_use] from portable-simd

[dtolnay]

These lines were missed in f3515fb/#136923 because core_simd/src/masks/bitmask.rs is only conditionally compiled.

rust/library/portable-simd/crates/core_simd/src/masks.rs

Lines 9 to 13 in 25d319a

	#[cfg_attr(
	all(target_arch = "x86_64", target_feature = "avx512f"),
	path = "masks/bitmask.rs"
	)]
	mod mask_impl;

Removing them unblocks bootstrapping rustc in an environment where avx512f is enabled. Without this change:

error: `#[must_use]` attribute cannot be used on trait methods in impl blocks
   --> library/core/src/../../portable-simd/crates/core_simd/src/masks/bitmask.rs:173:5
    |
173 |     #[must_use = "method returns a new mask and does not mutate the original value"]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = help: `#[must_use]` can be applied to data types, functions, unions, required trait methods, provided trait methods, inherent methods, foreign functions, and traits
    = note: `-D unused-attributes` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(unused_attributes)]`

To reproduce:

RUSTC_BOOTSTRAP=1 RUSTFLAGS=-Ctarget-feature=+avx512f cargo +nightly check --manifest-path=library/portable-simd/crates/core_simd/Cargo.toml --target=x86_64-unknown-linux-gnu --no-default-features

[rustbot]

Portable SIMD is developed in its own repository. If possible, consider making this change to rust-lang/portable-simd instead.

cc @calebzulawski, @programmerjake

[rustbot]

r? @Mark-Simulacrum

rustbot has assigned @Mark-Simulacrum.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[calebzulawski]

@bors r+

[bors]

📌 Commit c8d1ac9 has been approved by calebzulawski

It is now in the queue for this repository.