raylib: cherry-pick fix for setting feature macros

[michaellass]

When trying to build musializer, I encountered the following error:

In file included from ./raylib/raylib-5.0/src/rglfw.c:87:
./raylib/raylib-5.0/src/external/glfw/src/posix_poll.c: In function '_glfwPollPOSIX':
./raylib/raylib-5.0/src/external/glfw/src/posix_poll.c:49:32: error: implicit declaration of function 'ppoll'; did you mean 'poll'? [-Wimplicit-function-declaration]
   49 |             const int result = ppoll(fds, count, &ts, NULL);
      |                                ^~~~~
      |                                poll

It turns out that raylib has a fix for this in master (raysan5/raylib@192f7f1). Applying it fixed the issue for me.

This fixes the issue underlying #20.