With this flag (off by default), all of the dependencies are packaged
into the source archive (including SDL2 etc).
Useful for building on machines without an internet connection.
1. Platform and toolchain files are now all under `platforms/`, with a
single `CMake/platforms/${platform}.cmake` per platform.
2. Custom functions/macros are under `functions/`.
3. Finder modules are in `/finders`.
Gleb Mazovetskiy
Jmgr
Jonathan Mercier-Ganady