Improve resuming of failed builds
I can't count the times I've run mkarchiso
and forgot about it only to find that gpg pinentry has timed out. Re-running mkarchiso
should not re-run mksquashfs
if the squashfs image was build succesfuly.
Since the build process (xorriso in this case specifically) uses SOURCE_DATE_EPOCH
, save it to a file and read it when an unfinished build is resumed.