obs-scripting CMakeList.txt expects SWIG, Python3 or Luajit to enable
scripting so in case of not finding just return and don't abort
the configuration
This adds build-time options for disabling the Lua and/or Python
scripting support in cases where users do not wish to build
it, but have the required libraries installed.
Makes it so that the scripting cmake variable ENABLE_SCRIPTING is a user
variable rather than a global internal cmake variable, and defers the
internal global cmake variable to SCRIPTING_ENABLED instead.
