Clean 3dnow (LLVM 19, Rust 1.82.0)

[ojeda]

Clean:

'-3dnow' is not a recognized feature for this target (ignoring feature)
'-3dnowa' is not a recognized feature for this target (ignoring feature)

since Rust 1.82.0 due to llvm/llvm-project#96246 in LLVM 19 (upgrade: rust-lang/rust#127513; cleanup on Rust side of their target feature in Rust 1.81.0: rust-lang/rust#127864).

Probably to be done conditionally with the upcoming RUSTC_VERSION support (or just removing it, since LLVM should not be generating the instructions anyway: rust-lang/rust#127864 (comment)).

Thanks @nikic for the ping!

[ojeda]

https://lore.kernel.org/rust-for-linux/20240806144558.114461-1-ojeda@kernel.org/