thisDir != projectDir as of Nimble 0.13.0.
In versions prior to 0.13.0, they returned the same value, making it valid to run `withDir projectDir() / "dependency"`. As of 0.13.0, either `thisDir() / "dependency"` or just `"dependency"` must be used. This, unfortunately, broke multiple packages of mine.

Behavior dating back to at least 2019:
```
thisDir()    /tmp/nimble_2138900/githubcom_kayabaNervemcminisketch
projectDir() /tmp/nimble_2138900/githubcom_kayabaNervemcminisketch
```

New behavior:
```
thisDir()    /tmp/nimble_2139158/githubcom_kayabaNervemcminisketch
projectDir() /tmp/nimblecache-330808066/mc_minisketch_3935108725
```