Support other platforms than Linux

[dfintha]

Currently, we pay no mind to other platforms than Linux. But there should be support for the Windows, macOS, and *BSD systems, too.

Non-goals: Using MSVC or other compiler suites for Windows!

On Windows, we'd also use GCC or Clang, or the MinGW cross-compiler. This would require MSYS or Cygwin, however, that is not a problem. On macOS, we can only use the LLVM suite, however, it is available after installing the command-line developer tools. Finally, *BSD systems should have little to no difference to Linux systems from our aspect.

Each scenario must be tested, even if only on a virtual machine.

[dfintha]

The most important things here are the following.

• Path separators,
• executable paths, and
• object file formats.