There are some leftovers of the no-longer-existing "platform-intrinsic" ABI in RA

[RalfJung]

Grepping for PlatformIntrinsic and platform-intrinsic shows some results; this can all be removed -- that ABI does not exist any more.

[Veykril]

When were the last mentions in the standard libraries of these removed? We need to carry the support code for them for a bit longer I imagine.

[RalfJung]

Looks like that was in rust-lang/stdarch@56087ea, which probably propagated to the rustc repo shortly thereafter.

[RalfJung]

The Rust compiler itself removed support for them in rust-lang/rust#121516, so at that point (Feb 27th, 2024) they were definitely gone from the standard library.

[Veykril]

Okay then its safe for us to remove