Running abuild on the host directly creates directories in the
aport where it gets built. Interrupting abuild results in those
working-dirs not getting deleted.
We don't want to copy those entries to our builder.
It's only really noticeable if pmbootstrap tries to copy a broken
symlink in src/ and thus fails.
Reviewed-by: Oliver Smith <ollieparanoid@postmarketos.org>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20221207205201.22139-1-jane400@bingo-ev.de%3E
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