Windows failure on re-gen-modules-test (mega-regex)

re-gen-modules-test is failing on Windows in-place testing (on AppVeyor) with:
```
re-gen-modules-test.exe: src/Text/RE/TDFA/ByteString/Lazy.hs: openBinaryFile: does not exist (No such file or directory)
```

Looks like Windows git does not support symbolic links.