[thomasbuilds]

The posix_memalign check added in #317 only sets a CMake variable so HAVE_POSIX_MEMALIGN is never defined and rx_aligned_alloc still falls back to malloc in the portable fallback of intrin_portable.h (RISC-V, s390x, 32-bit ARM, ...). The cache, dataset, scratchpad and VM then only get malloc's alignment instead of 64 bytes. With -fsanitize=alignment on RISC-V, randomx-benchmark --verify --jit --softAes --threads 2 reports:

src/randomx.cpp:247:53: runtime error: constructor call on misaligned address 0x5555555f1610 for type 'struct CompiledLightVmDefault', which requires 64 byte alignment

On 32-bit ARM, glibc's malloc only guarantees 8-byte alignment, and Clang's NEON code in randomx_vm::initialize() (vld1.64 {d18, d19}, [r1:128]!) crashes with SIGBUS when the VM is not 16-byte aligned.

This defines it when the check passes, as is done for HAVE_HWCAP.