Could be that php.exe sees a commandline switch with a single dash as for him instead of for the php script, so it isn't passed on.
You could probably test that with "php oil -v -l" (small letter V, small letter L).
If they are passed to oil, you should see "Fuel: 1.9-dev running in "development" mode" (or whatever your Fuel version is).
If php grabs it, you should see either "No syntax errors detected in oil" if it only grabs the "-l", or "PHP 7.0.16 (cli) (built: Feb 15 2017 07:52:47) ( NTS )" or whatever your PHP version is, if it also grabs the "-v".