remove miri-test-libstd hacks that are no longer needed

Author: RalfJung

library/alloc/src/lib.rs

@@ -56,11 +56,6 @@
 //! [`Rc`]: rc
 //! [`RefCell`]: core::cell
 
-// To run alloc tests without x.py without ending up with two copies of alloc, Miri needs to be
-// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
-// rustc itself never sets the feature, so this line has no effect there.
-#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
-//
 #![allow(unused_attributes)]
 #![stable(feature = "alloc", since = "1.36.0")]
 #![doc(
@@ -71,7 +66,6 @@
 #![doc(cfg_hide(
     not(test),
     not(any(test, bootstrap)),
-    any(not(feature = "miri-test-libstd"), test, doctest),
     no_global_oom_handling,
     not(no_global_oom_handling),
     not(no_rc),

library/core/src/lib.rs

@@ -57,10 +57,7 @@
 //
 // This cfg won't affect doc tests.
 #![cfg(not(test))]
-// To run core tests without x.py without ending up with two copies of core, Miri needs to be
-// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
-// rustc itself never sets the feature, so this line has no effect there.
-#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
+//
 #![stable(feature = "core", since = "1.6.0")]
 #![doc(
     html_playground_url = "https://play.rust-lang.org/",
@@ -71,7 +68,6 @@
 #![doc(rust_logo)]
 #![doc(cfg_hide(
     not(test),
-    any(not(feature = "miri-test-libstd"), test, doctest),
     no_fp_fmt_parse,
     target_pointer_width = "16",
     target_pointer_width = "32",

library/std/src/lib.rs

@@ -212,13 +212,7 @@
 //! [rust-discord]: https://discord.gg/rust-lang
 //! [array]: prim@array
 //! [slice]: prim@slice
-// To run std tests without x.py without ending up with two copies of std, Miri needs to be
-// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
-// rustc itself never sets the feature, so this line has no effect there.
-#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
-// miri-test-libstd also prefers to make std use the sysroot versions of the dependencies.
-#![cfg_attr(feature = "miri-test-libstd", feature(rustc_private))]
-//
+
 #![cfg_attr(not(feature = "restricted-std"), stable(feature = "rust1", since = "1.0.0"))]
 #![cfg_attr(feature = "restricted-std", unstable(feature = "restricted_std", issue = "none"))]
 #![cfg_attr(not(bootstrap), rustc_preserve_ub_checks)]