Auto merge of #140282 - matthiaskrgr:rollup-g6ze4jj, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #137653 (Deprecate the unstable `concat_idents!`)
 - #138957 (Update the index of Option to make the summary more comprehensive)
 - #140006 (ensure compiler existance of tools on the dist step)
 - #140143 (Move `sys::pal::os::Env` into `sys::env`)
 - #140202 (Make #![feature(let_chains)] bootstrap conditional in compiler/)
 - #140236 (norm nested aliases before evaluating the parent goal)
 - #140257 (Some drive-by housecleaning in `rustc_borrowck`)
 - #140278 (Don't use item name to look up associated item from trait item)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_attr_parsing/src/lib.rs

@@ -77,8 +77,8 @@
 
 // tidy-alphabetical-start
 #![allow(internal_features)]
+#![cfg_attr(bootstrap, feature(let_chains))]
 #![doc(rust_logo)]
-#![feature(let_chains)]
 #![feature(rustdoc_internals)]
 // tidy-alphabetical-end