Auto merge of rust-lang#103098 - Amanieu:asm-tied-fixed, r=bjorn3

asm: Match clang behavior for inlateout fixed register operands

We have 2 options for representing LLVM constraints for `inlateout` operands on a fixed register (e.g. `r0`): `={r0},0` or `={r0},{r0}`.

This PR changes the behavior to the latter, which matches the behavior of Clang since https://reviews.llvm.org/D87279.

Author: bors