www/firefox: unbreak custom CPUTYPE with Rust 1.24

error[E0442]: intrinsic return value has wrong type: found vector with length 32, expected length 4

--> third_party/rust/simd/src/x86/avx2.rs:45:5
 |

45 | fn x86_mm256_sad_epu8(x: u8x32, y: u8x32) -> u8x32;

|     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

PR: 225582