openssl: check for conf file

Closes #34728.
It is consistently (in every bottle I've tested so far) missing ``` openssl.cnf ```, which causes OpenSSL and LibreSSL to throw big errors every time you use them. ``` openssl.cnf ``` is created when you build from source, but if you never build from source, you never get a ``` openssl.cnf ``` file in ``` HOMEBREW_PREFIX/etc/openssl ```.