Auto merge of #135832 - Kobzol:rustdoc-lto, r=onur-ozkan

Apply LTO config to rustdoc

Before, the LTO configuration from `config.toml` was not applied to `rustdoc`. This provides a small perf. and binary size [win](rust-lang/rust#112049 (comment)) for doc builds.

Since this is configured with Cargo profiles and not rustflags, it should not break tool build cache (rust-lang/rust#131155). I tried to run `x test miri`, `x test rustdoc` and `x test miri` and nothing was rebuilt.

r? `@onur-ozkan`

Author: bors