selftests/fchmodat2: clean up temporary files and directories

selftests/fchmodat2: clean up temporary files and directories

Patch series "selftests/fchmodat2: Error handling and general", v4.

I looked at the fchmodat2() tests since I've been experiencing some random
intermittent segfaults with them in my test systems, while doing so I
noticed these two issues.  Unfortunately I didn't figure out the original
yet, unless I managed to fix it unwittingly.

This patch (of 2):

The fchmodat2() test program creates a temporary directory with a file and
a symlink for every test it runs but never cleans these up, resulting in
${TMPDIR} getting left with stale files after every run.  Restructure the
program a bit to ensure that we clean these up, this is more invasive than
it might otherwise be due to the extensive use of ksft_exit_fail_msg() in
the program.

As a side effect this also ensures that we report a consistent test name
for the tests and always try both tests even if they are skipped.

Link: https://lkml.kernel.org/r/20260226-selftests-fchmodat2-v4-0-a6419435f2e8@kernel.org
Link: https://lkml.kernel.org/r/20260226-selftests-fchmodat2-v4-1-a6419435f2e8@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Alexey Gladkov <legion@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>