__builtin_memcpy, as well as __builtin_memset and __builtin_memmove, needn't be
inlined but emitted as a libc call, leading to infinitely recursive calls.
Fixes https://github.com/libsdl-org/SDL/issues/9090
Modern C runtimes have well optimized memset and memcpy, so use those instead of dispatching into SDL's versions. In addition, some compilers can analyze memset and memcpy calls and directly turn them into optimized assembly.