All dependency projects are now separated into their own Premake scripts and are designed to provide easy "import", "includes" and "setup" functions.
First, you use project.setup { ... } to provide the library with its respective configuration, this MAY include defines and MUST include the source path of that specific library. Then you can use project.includes() or project.import() in your target application or library project to let the script configure your project. This will configure all necessary include directories and links.