Fix macOS compilation for x86 (32-bits)

[AldoMX]

Historical Context

When I started StepMania AMX more than 15 years ago, I didn't know how code or use source control. This repo is an attempt to reconstruct the timeline, so I will be rewriting history and force pushing changes.

I have attempted to build the game in macOS, but I have never attempted to fix the build, so I don't know the amount of effort required to fix it.

What needs to be done?

Review each one of the ~ 600 commits, and update the macOS build files to apply changes in the exact point in time where they were introduced.

Attempt to build the project in High Sierra (2016), and depending on the effort to fix it attempt to backport the fixes to the earliest possible point in time.

Concerns

Apple deprecated OpenGL in Mojave (2017) and killed 32-bit support in Catalina (2018). I don't have the knowledge, neither I'm willing to write a Metal or Vulcan backend. But I might want to create an SDL2 backend.

Not even the official StepMania seems to run after Catalina so fixing the build may not be possible at all. I will also have to consider if it will be possible at all to build the project for Apple Silicon.

It seems that it will be easier to first fix the build for Windows ARMv7 (#11), AMD64 (#12) and ARMv8 (#13) first, then for Linux x86 (#7), ARMv7 (#14), AMD64 (#15) and ARMv8 (#16), and finally start the work on macOS x86 (this ticket).