After checking out, LuaAV can be built as follows:
cd buildtool ./scripts/install_dependencies.sh lua build.linux.lua ../
You will need Xcode/developer tools installed, with support for the OSX 10.5 SDK.
Open buildtool/osx/luaavmake.xcodeproj and build the Build target. This will build the buildtool and then run build.osx.lua. Any errors will show up in the build results pane of Xcode. Note – it may take quite a while to build!