PR 5786 revealed that the only git submodule that is left in this repo is the src/libpsl-native/test/googletest submodule and @iSazonov pointed out that we could maybe replace it with the following NuGet package:
https://www.nuget.org/packages/googletest/
The only caveat is that the current submodule is from September 2013 (version 1.7), which means the newer NuGet package (first version in October 2016, version 1.8) might contain breaking changes.