Old `executable-path` relies on internals of Cargo and will break with existing / upcoming features

Tests assumes the location of build artifacts
- This isn't the case when a user sets `build.build-dir` (added as of Cargo 1.91)
- This isn't the case if we approve the new `build-dir` layout (https://github.com/rust-lang/cargo/issues/15010)
- This isn't the case if we change the `build.build-dir` default (https://github.com/rust-lang/cargo/issues/16147)

You can reproduce this by running either:
```console
$ cargo +nightly test -Zbuild-dir-new-layout
$ CARGO_BUILD_BUILD_DIR=build cargo test
```

Upgrade to the latest version of `executable-path` for it to work (https://github.com/casey/executable-path/issues/2).

This problem was identified by the following crater run: https://github.com/rust-lang/rust/pull/149852