objdump return code regression

[bmwiedemann]

I noticed that 15-SP4's grub was reported as having 2 identical builds when there was plenty relevant objdump output.

git bisect pointed to

38e7800e76be477b222ff85d368c12fb179183dc is the first bad commit
commit 38e7800e76be477b222ff85d368c12fb179183dc
Author: Olaf Hering <olaf@aepfle>
Date:   Sun Mar 6 12:15:16 2022 +0100

    fix ELF comparision to really show disasm output

    Also be more specific about the old/new path.

    Fixes commit e4c745cbb083481a67e852e95f5dd93ff94a82fa

that screwed up the return code.

[bmwiedemann]

Turther testing showed that it is the first elfdiff= that breaks the return code.

[olafhering]

Do you have a test case?
elfdiff seems to be indicate failure in all cases.
Tthe variable objdump_failed could be removed, as it indicates some failure in the same way as elfdiff.