folly +tests needs a better fix for aligned_alloc on macOS <11; perhaps, switch to posix_memalign

[barracuda156]

/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_devel_folly/folly/work/folly-v2024.01.22.00/folly/hash/test/ChecksumBenchmark.cpp:68:31: error: no member named 'aligned_alloc' in namespace 'std'; did you mean simply 'aligned_alloc'?
  buf = static_cast<uint8_t*>(std::aligned_alloc(4096, kBufSize + 64));
                              ^~~~~~~~~~~~~~~~~~
                              aligned_alloc
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/malloc/_malloc.h:50:10: note: 'aligned_alloc' declared here
void    *aligned_alloc(size_t __alignment, size_t __size) __result_use_check __alloc_size(2) __OSX_AVAILABLE(10.15) __IOS_AVAILABLE(13.0) __TVOS_AVAILABLE(13.0) __WATCHOS_AVAILABLE(6.0);
         ^
1 error generated.

I will deal with this, but not rightaway today, so ticket is justified.

Also, my initial fix, while allows it to build on some old systems (fixed it for me on 10.6), does not behave in a way folly expects, so it should be perhaps changed to use posix_memalign.