Rename `optin_builtin_traits` to `auto_traits`

They were originally called "opt-in, built-in traits" (OIBITs), but
people realized that the name was too confusing and a mouthful, and so
they were renamed to just "auto traits". The feature flag's name wasn't
updated, though, so that's what this PR does.

There are some other spots in the compiler that still refer to OIBITs,
but I don't think changing those now is worth it since they are internal
and not particularly relevant to this PR.

Also see <https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/opt-in.2C.20built-in.20traits.20(auto.20traits).20feature.20name>.

2 files changed, 9 insertions, 3 deletions

diff --git a/library/rtstartup/rsbegin.rs b/library/rtstartup/rsbegin.rs
index bd1946133e8..b64f13dba4c 100644
--- a/library/rtstartup/rsbegin.rs
+++ b/library/rtstartup/rsbegin.rs
@@ -9,10 +9,13 @@
 // headers or footers.
 //
 // Note that the actual module entry point is located in the C runtime startup
-// object (usually called `crtX.o), which then invokes initialization callbacks
+// object (usually called `crtX.o`), which then invokes initialization callbacks
 // of other runtime components (registered via yet another special image section).
 
-#![feature(no_core, lang_items, optin_builtin_traits)]
+#![feature(no_core)]
+#![feature(lang_items)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![crate_type = "rlib"]
 #![no_core]
 #![allow(non_camel_case_types)]
diff --git a/library/rtstartup/rsend.rs b/library/rtstartup/rsend.rs
index 333761cd977..18ee7c19ba0 100644
--- a/library/rtstartup/rsend.rs
+++ b/library/rtstartup/rsend.rs
@@ -1,6 +1,9 @@
 // See rsbegin.rs for details.
 
-#![feature(no_core, lang_items, optin_builtin_traits)]
+#![feature(no_core)]
+#![feature(lang_items)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![crate_type = "rlib"]
 #![no_core]