Exports LR_EXTERNAL and LUA environment variables.
Exports LR_EXTERNAL and LUA environment variables.

- LR_EXTERNAL: The folder where LuaRocks will look for external dependencies.
- LUA: The name of the intepreter (either lua or luajit)

ignacio/lua-appveyor-example,xpol/lua-appveyor-example,starius/lua-appveyor-example