Build std with panic = "abort" errors with a bunch of duplicated lang items

[xTachyon]

Code

[profile.release]
panic = "abort"

rustup run nightly-2023-09-17 cargo rustc -p dune --profile release -Z build-std=std,core --target x86_64-pc-windows-msvc

The nightly version is not important, it's only what I was testing on.

Current output

A bunch of these:

error[E0152]: duplicate lang item in crate `core`: `sized`.
  |
  = note: the lang item is first defined in crate `core` (which `std` depends on)
  = note: first definition in `core` loaded from \\?\D:\repos\dune\target\x86_64-pc-windows-msvc\release\deps\libcore-8e933d06c178c4de.rlib, \\?\D:\repos\dune\target\x86_64-pc-windows-msvc\release\deps\libcore-8e933d06c178c4de.rmeta
  = note: second definition in `core` loaded from \\?\C:\Users\tachyon\.rustup\toolchains\nightly-2023-08-17-x86_64-pc-windows-msvc\lib\rustlib\x86_64-pc-windows-msvc\lib\libcore-b86a9ba077d96bbb.rlib

Desired output

A nice message that said panic_abort must be included in build-std if compiled with panic = "abort".

Rationale and extra context

From @Nilstrieb:
rustc can't find a panic_abort in your self-built standard library, so it falls back to loading panic_abort from the sysroot. But that sysroot panic_abort then also brings in the rest of the sysroot, including core, so now you have two cores, one from your target dir and one from your sysroot. This is bad.

Other cases

No response

Anything else?

No response

[Noratrieb]

Probably makes sense to have a specialized error message when loading core twice.

[klensy]

rust-lang/wg-cargo-std-aware#56, rust-lang/wg-cargo-std-aware#29