rebuild_PC: support more systems (Mingw and Linux)

[PedroHLC]

• Add Makefile and code changes allowing to build for:
  • Mingw32 GCC
  • Mingw32 CLANG
  • i686 Linux GCC
  • i686 Linux Clang
• They all build and generate proper artifacts right now, but only playable in:
  • i686 Linux GCC
  • i686 Linux Clang
• Includes Nix scripts and/or Flake for helping to build everything;
• Includes a rebuild_PC/README.md detailing requirement to build;
• Prints where memory starts to help debugging;
• Prints the compiler to help debugging;
• Prints the state of USE_16BY9to help debugging;
• Includes an .editorconfig so I don't mess with yours NL at EOF;
• math.h needed to be renamed to ctr_math.h to stop conflicting with standard library's one;
• Other values then 0x00D00000 works, but some corrupt the PE generated by Mingw32 GCC, and others corrupt Clang's ELF;
• All the patching done in PsyCross was sent for reviewing in enhance gcc/mingw 32/64 support OpenDriver2/PsyCross#9
• Includes a CI that builds these 4 environments.