Flaky test misc/support_collect fails on --work-dir step

@wkz

One failing test on styx:

2025-12-03 16:03:42 # Starting (2025-12-03 16:03:42)
2025-12-03 16:03:42 # host:    monza
2025-12-03 16:03:42 #     mgmt:    sw1p1
2025-12-03 16:03:42 # target:  styx1
2025-12-03 16:03:42 #     mgmt:    e28
2025-12-03 16:03:42 #
2025-12-03 16:03:42 # Waiting for DUTs to become reachable...
2025-12-03 16:03:42 # Probing styx1 on port sw1p1 for IPv6LL mgmt address ...
2025-12-03 16:03:42 # Testing using NETCONF
2025-12-03 16:03:42 # Connecting to mgmt IP fe80::96de:eff:fe05:2614%sw1p1:830 ...
2025-12-03 16:03:42 # YANG models downloaded.
2025-12-03 16:03:44 # Waiting for DUTs to become reachable...
2025-12-03 16:03:44 # Probing styx1 on port sw1p1 for IPv6LL mgmt address ...
2025-12-03 16:03:44 ok 1 - Set up topology and attach to target DUT
2025-12-03 16:03:44 # GPG not available on target - skipping encryption tests
2025-12-03 16:03:44 ok 2 - Check for GPG availability on target
2025-12-03 16:03:44 # support collect failed with return code 255
2025-12-03 16:03:44 # stderr:
2025-12-03 16:03:44 not ok 3 - Run support collect with --work-dir and short log tail
2025-12-03 16:03:44 # Exiting (2025-12-03 16:03:44)
2025-12-03 16:03:44 # Traceback (most recent call last):
2025-12-03 16:03:44 #   File "/home/styx/.ghmoon/kernelkit/infix/git/test/case/misc/support_collect/test.py", line 51, in <module>
2025-12-03 16:03:44 #     raise Exception("support collect command failed")
2025-12-03 16:03:44 # Exception: support collect command failed
2025-12-03 16:03:44 #
test error, no plan

Not sure what happened there (or why the report was not uploaded). But seems more likely to be some flaky thing in the test (given that it was added very recently).

Originally posted by @wkz in #1267 (comment)

support: diagnostic debug for flaky test

support: bound each command, keep the log on failure, add --output