Unbreak usr.bin/dc with OpenSSL 3

[ngie]

Summary

OpenSSL's BN_zero API has had a void return value since 1.1.x: chase the
change to unbreak the build on OpenSSL 3.x with MK_GH_BC == no.

MFC after: 2 weeks

[se]

The patch seems correct, but this dc implementation is not built by default on FreeBSD-13 or later, and thus only relevant for STABLE-12 (unless WITHOUT_GH_BC is defined, preventing the build of Gavin D. Howards much improved bc and dc programs). It is therefore definitely relevant for STABLE-12, but a NOP on STABLE-13 and CURRENT built with default options.

[ngie]

In D41410#942912, @se wrote:

The patch seems correct, but this dc implementation is not built by default on FreeBSD-13 or later, and thus only relevant for STABLE-12 (unless WITHOUT_GH_BC is defined, preventing the build of Gavin D. Howards much improved bc and dc programs). It is therefore definitely relevant for STABLE-12, but a NOP on STABLE-13 and CURRENT built with default options.

I agree, but what's the point of shipping software with FreeBSD that doesn't compile?

[kevans]

+1, if we're still offering it as a build knob we need to either fix it or remove it.