01cd24c226 doc: set CC_FOR_BUILD when building on OpenBSD (fanquake)
Pull request description:
Closes: #19559
While #19559 has been fixed upstream, it makes sense to not only
recommend using `CC_FOR_BUILD`here until the fix is pulled in as
part of our next libsecp update, but after discussing with Cory,
he suggested we should be setting this on OpenBSD (which still has
the an ancient GCC) regardless.
ACKs for top commit:
real-or-random:
ACK 01cd24c226 I looked at the diff (but can't test the instructions on OpenBSD)
laanwj:
Code review ACK 01cd24c226
Tree-SHA512: 322802b9303771f1be2ad9628f268dfa71dc7ee77948fa2a34f21eceb19b2d8efdd8876c8f0778adbfcde48fa0f88cd4e698ae425428159abca38e8c7980da1d