tests: add coverage to ensure Wix tracks 'help' and 'templates' files This would have caught the problem fixed by 65d2538ac993. There are other *.wxs files that can be checked, but they appear to be more complicated. For example, locale.wxs has what appears to be foreach loop support, as well as variable substitution. By checking `hg files` to determine tracked file, this is able to avoid false failures when other junk is present in the filesystem, like *.orig files. I can't tell if the map-cmdline.status file is not included on purpose, but I don't see the purpose of excluding it. The missing help files seem reasonable for Windows.