Adjust the std library for sanitizer_cfi cfgs changes

Author: Urgau

library/std/src/lib.rs

@@ -265,6 +265,7 @@
 //
 // Language features:
 // tidy-alphabetical-start
+#![cfg_attr(not(bootstrap), feature(cfg_sanitizer_cfi))]
 #![feature(alloc_error_handler)]
 #![feature(allocator_internals)]
 #![feature(allow_internal_unsafe)]

library/std/src/sys/unix/thread_local_dtor.rs

@@ -11,7 +11,7 @@
 // Note, however, that we run on lots older linuxes, as well as cross
 // compiling from a newer linux to an older linux, so we also have a
 // fallback implementation to use as well.
-#[allow(unexpected_cfgs)]
+#[cfg_attr(bootstrap, allow(unexpected_cfgs))]
 #[cfg(any(
     target_os = "linux",
     target_os = "android",