Added Linux build

I had someone ask for a Linux build, and since I have been a long time Linux user myself I decided to go ahead and do it. I tested it on the latest stable builds of Ubuntu (18.04) and Manjaro (18.1.3). There are a couple of dependencies that will need to be installed according to the GameMaker help site, but these were already installed on both of the distros I tried.

libcurl4
libopenal1