Auto merge of #46528 - CensoredUsername:stabilize_abi_sysv64, r=arielb1

Stabilize abi_sysv64

Closes #36167, stabilizing the use of the "sysv64" ABI on x64 platforms where it is not the default ABI.

FCP on this is complete in the tracking issue.

src/test/codegen/abi-sysv64.rs

@@ -18,7 +18,6 @@
 // compile-flags: -C no-prepopulate-passes
 
 #![crate_type = "lib"]
-#![feature(abi_sysv64)]
 
 // CHECK: define x86_64_sysvcc i64 @has_sysv64_abi
 #[no_mangle]

src/test/compile-fail/feature-gate-abi-sysv64.rs

@@ -1,19 +0,0 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-// Test that the sysv64 ABI cannot be used when abi-sysv64 feature
-// gate is not used.
-
-extern "sysv64" fn foo() {}
-//~^ ERROR sysv64 ABI is experimental and subject to change
-
-fn main() {
-    foo();
-}

src/test/run-pass/abi-sysv64-arg-passing.rs

@@ -39,7 +39,6 @@
 
 // note: windows is ignored as rust_test_helpers does not have the sysv64 abi on windows
 
-#![feature(abi_sysv64)]
 #[allow(dead_code)]
 #[allow(improper_ctypes)]
 

src/test/run-pass/abi-sysv64-register-usage.rs

@@ -15,7 +15,6 @@
 // ignore-arm
 // ignore-aarch64
 
-#![feature(abi_sysv64)]
 #![feature(asm)]
 
 #[cfg(target_arch = "x86_64")]