The flatbuffers library is a serialization library, created by Google
for game development and performance-critical applications.
It aims to be fast and efficient.
This commit creates a port of it to SerenityOS.
The flatbuffers build process generates three things: some header files,
a library (libflatbuffers) and a schema compiler (flatc).
There are tests, but they are not compiled, because it runs the
flatbuffers schema compiler, one of the things we are cross-compiling.
The compiler will not run because the target is different from the host
