Auto merge of #127731 - veluca93:abi_checks, r=RalfJung

Emit future-incompatibility lint when calling/declaring functions with vectors that require missing target feature

On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.)

As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code.

This commit makes it a post-monomorphization error to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI.

See the [nomination comment](rust-lang/rust#127731 (comment)) for more discussion.

r? RalfJung

Part of rust-lang/rust#116558

Author: bors