Yes, binaries, C sources and build scripts must be included (see faq). There should be no external dependencies except for system libs.
Dunno about drone.io. The way I build for multiple platforms is by having virtualbox images for all OSs. For OSX I just use my Mac because these fuckers don't allow OSX on a VM. For more see https://luapower.com/building
The .so and .a files (so libfoo.so and libfoo.a).
You can compile for both 32bit and 64bit on any Mac (clang is a cross-compiler). You just need to set the appropriate flags. For more see https://luapower.com/build-scripts
You can put luapower wherever you like (certainly not in /usr/local/bin), mgit will work from any directory where there's a .mgit folder, just like git looks for the .git folder.
Not at all. These are good questions, keep'em coming.