build: Silence deprecation warnings from OpenSSL 3

build: Silence deprecation warnings from OpenSSL 3

The OpenSSL developers suggest that anyone wishing to continue using
low-level functions may either live with the warnings, silence them,
or switch to high level functions.

As high level functions do their own memory allocation, switching to
them may lead to performance regressions.

We do not wish to have deprecation warnings filling up our compiler
outputs when searching for other messages.

So silencing the warnings, at least for now, seems the least bad option.

Signed-off-by: Adam C. Emerson <aemerson@redhat.com>
(cherry picked from commit d5e1fdfc3cfd15b59e0e8fe2408c995b0cc8c0e7)