Temporary directories not cleaned

[joelberkeley]

Looks like pack's not tidying temporary directories. I often Ctrl+C mid-install, might be the cause

$ ls .pack/
bin/     db/      .tmp0/   .tmp10/  .tmp12/  .tmp14/  .tmp16/  .tmp18/  .tmp2/   .tmp21/  .tmp4/   .tmp6/   .tmp8/   user/
.cache/  install/ .tmp1/   .tmp11/  .tmp13/  .tmp15/  .tmp17/  .tmp19/  .tmp20/  .tmp3/   .tmp5/   .tmp7/   .tmp9/