4a5c49363a added some more commands after
`extraPostFetch` but concatenated them without a separating newline.
Which means, that since that commit
fetchzip { ..., extraPostFetch = ''rm -f "$out"/some-file''; }
now actually runs the following shell command
rm -f "$out"/some-file"chmod -R a-w "$out"
thus deleting "$out". Which is very unfortunate.
Especially since this actually happens on master for all `fetchFromBitbucket`
derivations. But since the results are fixed-output users bulding with hydra
cache enabled are not hitting this for not recently updated derivations yet.