Rollup merge of #142464 - RalfJung:variadic-fn-abi-error, r=workingjubilee

variadic functions: remove list of supported ABIs from error

I think this list is problematic for multiple reasons:
- It is bound to go out-of-date as it is in a very different place from where we actually define which functions support varagrs (`fn supports_varargs`).
- Many of the ABIs we list only work on some targets; it makes no sense to mention "aapcs" as a possible ABI when building for x86_64. (This led to a lot of confusion in https://github.com/rust-lang/rust/issues/110505 where the author thought they should use "cdecl" and then were promptly told that "cdecl" is not a legal ABI on their target.)
- Typically, when the programmer wrote `extern "foobar"`, it is because they need the "foobar" ABI. It is of little use to tell them that there are other ABIs with which varargs would work.

Cc ``@workingjubilee``

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/ui/error-codes/E0045.stderr b/tests/ui/error-codes/E0045.stderr
index b8ee31a4049..ecf5f4e0182 100644
--- a/tests/ui/error-codes/E0045.stderr
+++ b/tests/ui/error-codes/E0045.stderr
@@ -1,4 +1,4 @@
-error[E0045]: C-variadic function must have a compatible calling convention, like `C`, `cdecl`, `system`, `aapcs`, `win64`, `sysv64` or `efiapi`
+error[E0045]: C-variadic functions with the "Rust" calling convention are not supported
   --> $DIR/E0045.rs:1:17
    |
 LL | extern "Rust" { fn foo(x: u8, ...); }