a60600e0af
Currently (or when testing any shell that does not support -X) the test will be skipped (also for [m]ksh (but not ksh93 etc) where there is an absurdly badly named -X option, skip the new test for them as well.) When -X appears in /bin/sh, this will verify that it is probably working (the test is MUCH more gruelling than any rational use of -X would be.)