Without going through an intricate dance with git to change the remote
URL of a repository, it's simplest to just nuke the cloned folder, as
we have to do a clean clone anyway.

The documentation states that users can override where to take a
dependency from via variables like VULKAN_HEADERS_INSTALL_DIR, however
the helper.cmake written by the scripts/CMakeLists.txt FORCE updates
the cache variable to the location inside known_good.json, practically
overwriting the user-provided path given on the CLI using -D, also
going into the cache.