adjustments to objdump call

[GitMensch]

After recognizing that the process path of objdump is resolved first, I've adjusted the PR to use that (so the additional stat calls seen in #527 are not needed).

• invoke directly from the processPath already resolved before
• improve error message for objdump invocation issues helping to find problems related to the call

[lievenhey]

@GitMensch lgtm, but can you ran clang-format so that the ci no longer complains?

[GitMensch]

applied clang-format -i and pushed

[GitMensch]

• string puzzle fixed, other invocations of error messages changed accordingly
• additional commit fixing a related issue (missing check -> error message)

[GitMensch]

rebased and split from 2 to 3 separate commits (I do like the result more than the original, too); tested manually in the GUI using the files under "tests" (all but the timeout, checked this with the appImage and also works as expected).

Adjusted one test as needed and added some of the missing tests for the adjusted messages.

[milianw]

thanks!