test: fix test-child-process-spawn-typeerror
test: fix test-child-process-spawn-typeerror

You cannot spawn 'dir' on Windows because it's not an executable.  Also,
some people might have 'ls' on their path on Windows, so I changed
invalidCmd to something that's highly unlikely to exist.

Reviewed-by: Trevor Norris <9cb5491eb5770dd8e0bf77a8a0335abf5f0488c5@gmail.com>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node