Auto merge of #77347 - jyn514:dox, r=Amanieu

Remove --cfg dox from rustdoc.rs

This was added in #53076 because
several dependencies were using `cfg(dox)` instead of `cfg(rustdoc)` (now `cfg(doc)`).
I ran `rg 'cfg\(dox\)'` on the source tree with no matches, so I think
this is now safe to remove.

r? `@Mark-Simulacrum`
cc `@QuietMisdreavus` :)

Author: bors

Diff for: library/stdarch

@@ -11,7 +11,6 @@ fn main() {
     let args = env::args_os().skip(1).collect::<Vec<_>>();
     let rustdoc = env::var_os("RUSTDOC_REAL").expect("RUSTDOC_REAL was not set");
     let libdir = env::var_os("RUSTDOC_LIBDIR").expect("RUSTDOC_LIBDIR was not set");
-    let stage = env::var("RUSTC_STAGE").expect("RUSTC_STAGE was not set");
     let sysroot = env::var_os("RUSTC_SYSROOT").expect("RUSTC_SYSROOT was not set");
 
     use std::str::FromStr;
@@ -24,14 +23,8 @@ fn main() {
     let mut dylib_path = bootstrap::util::dylib_path();
     dylib_path.insert(0, PathBuf::from(libdir.clone()));
 
-    //FIXME(misdreavus): once stdsimd uses cfg(doc) instead of cfg(dox), remove the `--cfg dox`
-    //arguments here
     let mut cmd = Command::new(rustdoc);
     cmd.args(&args)
-        .arg("--cfg")
-        .arg(format!("stage{}", stage))
-        .arg("--cfg")
-        .arg("dox")
         .arg("--sysroot")
         .arg(&sysroot)
         .env(bootstrap::util::dylib_path_var(), env::join_paths(&dylib_path).unwrap());