die on create-diff-object when all objects have processed

When working on large patches that are bound to have lots of
errors, it can be frustrating to have to re-run the build and wait
after every error you fix. With this patch, you get a chance to see
most (if not all) of the errors you'll be facing, at least across
the different object files.
Give more generic failure message, and include ERROR in output
Merge pull request #408 from cormander/show-all-errors

die on create-diff-object when all objects have processed