openssl: Prevent OpenSSL from using posix_memalign() if LD is enabled

openssl: Prevent OpenSSL from using posix_memalign() if LD is enabled

The leak detective doesn't wrap this function and calling the original
causes unknown memory frees and even segmentation faults.  This is now
triggered with OpenSSL 4 as the implementation of ECP256 uses
OPENSSL_aligned_alloc_array().

Setting a custom memory functions forces OpenSSL to implement aligned
allocations internally, using the registered allocation function.