Doctest suite built with GHC 8.10.4 doesn't finish on Windows

[sjakobi]

The dhall:doctest suite doesn't finish anymore since we've switched from GHC 8.6.5 to 8.10.4.

For example in https://github.com/dhall-lang/dhall-haskell/pull/2239/checks?check_run_id=3008625914#step:6:1500 you can see that doctest prints the final summary, but stack fails to report success as usual with

dhall> Test suite doctest passed

We've only observed this issue in GitHub Actions and on AppVeyor so far, but you should be able to reproduce this locally on a Windows machine with:

git clone https://github.com/dhall-lang/dhall-haskell
cd dhall-haskell
git checkout c23e4d55691bbec2cae6f809dece357de3153382
stack test dhall:doctest

[sjakobi]

Note that the doctest suites of the dhall-docs and dhall-lsp-server packages in the same project pass and finish as expected.

[sjakobi]

Any ideas what might be wrong?

Is it reasonable to assume that the actual test cases are passing (and not e.g. hanging), given the final summary

Examples: 252  Tried: 252  Errors: 0  Failures: 0

?