Auto merge of #146282 - tgross35:rollup-0n5tjnm, r=tgross35

Rollup of 5 pull requests

Successful merges:

 - rust-lang/rust#139524 (Add socket extensions for cygwin)
 - rust-lang/rust#145940 (single buffer for exponent fmt of integers)
 - rust-lang/rust#146206 (identity uses are ok, even if there are no defining uses)
 - rust-lang/rust#146272 (Update comment for `-Werror` on LLVM builds)
 - rust-lang/rust#146280 (Make `LetChainsPolicy` public for rustfmt usage)

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

Author: bors