Add an initial Platform module for SerenityOS. This module is a mix of the platform module currently used to build the Serenity Kernel and Userspace applications and libraries, and the platform module included in the CMake Port which still has some work to do on the system before its other patches could be considered for upstreaming.
As such, the platform module is currently only useful when used with a suitably patched GCC or LLVM cross-compiler toolchain.
Issue: #23589
Topic-rename: SerenityOS-platform