Prevent "Unsupported tarball" exception upon download of Git dependency containing problematic symlinks

[dynamicboid]

When Stack projects contain extra-dep Git dependencies that have certain problematic symlinks, stack will throw an error when building a project if it is unable to resolve those symlinks successfully. However, on subsequent invocations of Stack, it seems that Pantry is able to cache the Git artifacts and enable Stack to run successfully. This PR seeks to address the former issue of Stack failing upon the first invocation on such a project. This may thus partially address issues #4913, #5004 and #5603 on the Stack repository as well as #23 on the Haskell shower repo.

[mpilgrem]

Merged manually with d813274.

Rather than normalise getFiles, it seemed to me better to add normalisation to the ATZip limb of foldArchive, as foldTar already normalises the other two limbs.

[neilmayhew]

cc @philderbeast

[neuroevolutus]

@mpilgrem, thanks so much for taking the time to review this!