Unfortunately, sanitizers do not support versioned symbols[1],
so they break filesystem access via the legacy, pre-ino64 ABI.

To use sanitizers on FreeBSD >= 12, we need to build the libc
crate with LIBC_CI=1 to use the new ABI -- including the libc
used for std. But that removes the st_lspare field std was
expecting for the deprecated metadata extension.

Add a way to skip that field to allow the build to work.

[1]: google/sanitizers#628

…-obk

Add sanitizer support on FreeBSD

Restarting rust-lang#47337. Everything is better now, no more weird llvm problems, well not everything:

Unfortunately, the sanitizers don't have proper support for versioned symbols (google/sanitizers#628), so `libc`'s usage of `stat@FBSD_1.0` and so on explodes, e.g. in calling `std::fs::metadata`.

Building std (now easy thanks to cargo `-Zbuild-std`) and libc with `freebsd12/13` config via the `LIBC_CI=1` env variable is a good workaround…

```
LIBC_CI=1 RUSTFLAGS="-Z sanitizer=address" cargo +san-test -Zbuild-std run --target x86_64-unknown-freebsd --verbose
```

…*except* std won't build because there's no `st_lspare` in the ino64 version of the struct, so an std patch is required:

```diff
--- i/src/libstd/os/freebsd/fs.rs
+++ w/src/libstd/os/freebsd/fs.rs
@@ -66,8 +66,6 @@ pub trait MetadataExt {
     fn st_flags(&self) -> u32;
     #[stable(feature = "metadata_ext2", since = "1.8.0")]
     fn st_gen(&self) -> u32;
-    #[stable(feature = "metadata_ext2", since = "1.8.0")]
-    fn st_lspare(&self) -> u32;
 }

 #[stable(feature = "metadata_ext", since = "1.1.0")]
@@ -136,7 +134,4 @@ impl MetadataExt for Metadata {
     fn st_flags(&self) -> u32 {
         self.as_inner().as_inner().st_flags as u32
     }
-    fn st_lspare(&self) -> u32 {
-        self.as_inner().as_inner().st_lspare as u32
-    }
 }
```

I guess std could like.. detect that `libc` isn't built for the old ABI, and replace the implementation of `st_lspare` with a panic?

Rename HAIR to THIR (Typed HIR).

r? @nikomatsakis

Originally suggested by @eddyb

Remove `linked_list_extras` methods.

Removing these in favor of the `Cursor` API in rust-lang#58533 .
Closes rust-lang#27794.

r? @Amanieu

…Mark-Simulacrum

1.45.2 release notes

(for master)

cc rust-lang#74958