cmake: add some simple tests on windows platforms.
The main test harnesses are written in unix shell script, so they don't work on windows. A stanza was added to the cmake config to skip all tests there to get a green build. This is misleading, since no testing was done at all on Windows. Instead, construct a separate set of tests on non-unix platforms, calling the two api test programs, which of necessity are compiled executables. Also invoke the two front-end programs with just the --help switch to verify they at least start. Thanks to Marcus Asteborg for the suggestion.