If someone tries to build without git they need to set
OBS_VERSION_OVERRIDE, this makes the error message occur before things
like string parsing on the OBS_VERSION which look like missing
parameters.
Currently the Info.plist file names the app package as OBS.app and cmake
is trying to use 'OBS Studio.app'. I renamed it to OBS for the time
being just because we don't currently have actual studio interface yet.