Auto merge of #8996 - alexcrichton:revert, r=ehuss

Revert #8954 - changing rustdoc's cwd

This PR reverts https://github.com/rust-lang/cargo/pull/8954 in reference to https://github.com/rust-lang/cargo/issues/8993 and https://github.com/rust-lang/cargo/issues/8992 where there's still definitely a bug to be fixed but we should probably avoid regressing in the meantime.

Closes https://github.com/rust-lang/cargo/issues/8992