build, cmake: switch OPENSSL_CRYPTO_LIBRARY -> OPENSSL_CRYPTO_LIBRARIES

build, cmake: switch OPENSSL_CRYPTO_LIBRARY -> OPENSSL_CRYPTO_LIBRARIES

OPENSSL_CRYPTO_LIBRARY returns just the full path to libcrypto.a
OPENSSL_CRYPTO_LIBRARIES returns also any other libraries required to fully
link an executable with libcrypto.a. This can be -lpthread, or -ldl, or
something else.

The FindOpenSSL.cmake module does a good job of identifying these dependent
libs, but the OPENSSL_CRYPTO_LIBRARIES variable must be used (same as using
ZLIB_LIBRARIES).

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Reviewed-by: Petr Štetiar <ynezz@true.cz>