rm: fix error reporting for -r on Linux fixing #9011

[ChrisDryden]

This PR takes the commit from the previously made PR #9011 from @Arcterus. We already had integration tests made for this exact scenario but the validation in the integration test was not correct.

The high level idea is that uutils was overriding the error instead of using |= and when that is fixed only a single error is printed, which matches the GNU behavior

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/rm/rm1 (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/rm/rm1 (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/shuf/shuf-reservoir (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/sort/sort-stale-thread-mem (passes in this run but fails in the 'main' branch)