The --libdir switch got lost at some point, which is useful for running
tests with a system build.
Further allow to switch the type of output at runtime avoiding an
unnecessary rebuild.
Finally allow to specify an output file, this means there is no need to
redirect stdout which might break the CI in case the tests write
something to stdout like in case of LOGERROR resulting the test result
not being valid xml.
Ref: #7534
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
39ea3b6ea5