Fix failing tests in windows (reloaded)

[jneira]

• Using a patched version of cabal-helper (until the next release)
  • It includes the remove of the private lib
• Azure windows agent have changed their drives space now C: has lot of more space than D:, so i've switched again cache to C:
• Some of unit failing tests had been fixed by Set current working directory when executing project ghc #1654

[fendor]

LGTM, but why no git submodules? That was previously how we handled modified packages

[jneira]

mmm, i've found submodules more suited to mid or long term forks due to the additional effort to setup and maintain them, i hope this is a provisional workaround