Auto merge of #85344 - cbeuw:remap-across-cwd, r=michaelwoerister

Auto merge of #85344 - cbeuw:remap-across-cwd, r=michaelwoerister

Correctly handle remapping from path containing the current directory with trailing paths

If we have a `auxiliary/lib.rs`, and we generate the metadata with `--remap-path-prefix $PWD/auxiliary=xyz`, the path to `$PWD/auxiliary/lib.rs` won't be correctly remapped in the metadata. This is because internally, path to the working directory itself and relative paths to files under the working directory are remapped separately (hence neither are affected since neither has `$PWD/auxiliary` as prefix), but the concatenation between the working directory and the relative path is not remapped. This PR fixes that.