When helmfile.d contains multiple release files and one release has a
local chart dependency (e.g. chart: ../chart), the dependency path was
passed to DirectoryExistsAt without normalizing against basePath. This
caused the path to be resolved against CWD instead of the helmfile
directory, so the local chart was not detected and helmfile tried to
resolve it as a remote repo, failing with:
'failed reading adhoc dependencies: no helm list entry found for repository'
Fixes#2596
Signed-off-by: yxxhero <aiopsclub@163.com>