Quilt patch support

Anyone who has build RPMs or debs is familiar with a simple tool called quilt. It's main purpose is to safely create an ordered set of patches that can be applied and removed in a specified order. Unlike generating patch files from git, the patch names are not lexicographically named in the order which they should be applied; instead, a series file is added to the patch folder. This file simply lists the patch file names in the order in which they should be applied.

This pull request does two things:

1. If a series file is present, the patches (and their application order) is determined by the series file alone
2. This behavior is explained in the help text for ghcup compile ghc -h