Fix compilation on Apple
Always use the posix function posix_memalign() as aligned memory
allocator on Apple computers. This should allow to compile Stockfish
out of the box on all versions of Mac OS X.
Patch tested on the following systems (apart from the CI) :
• Mac OS 10.9.6 (arch x86-64-sse41-popcnt) with gcc-10
• Mac OS 10.13.6 (arch x86-64-bmi2) with gcc-10, gcc-14 and clang-11
• Mac OS 14.1.1 (arch apple-silicon) with clang-15
closes https://github.com/official-stockfish/Stockfish/pull/5462
No functional change