Rollup merge of #142285 - workingjubilee:dont-use-bad-assembly, r=nnethercote

tests: Do not run afoul of asm.validity.non-exhaustive in input-stats

This addresses one of the three powerpc64-unknown-linux-musl test failures in rust-lang/rust#142280

I was motivated to cover it myself because technically this is also compile-time UB if we compile a program that has `asm!` with x86-64-specific instructions on another platform. That'll only mean something if this is ever switched to build-pass, or if checking emits object code, but conveniently "nop" is valid assembly on all platforms anyone has implemented Rust codegen for. Even the weird ones LLVM doesn't support, like PA-RISC or Common Intermediate Language.

...except GPUs. Not sure about those.

r? ```@nnethercote```

Author: matthiaskrgr