acme.sh dnsapi/dns_edgedns.sh invokes iconv(1) which is not provided by
OpenBSD in the base system. Adding the libiconv package provides this tool.
This should also help address acmesh-official/acme.sh#4350, albeit indirectly:
it looks like that PR cannot be merged because the OpenBSD test fails despite
the PR not actually changing anything having to do with iconv. That is, I
suspect that the test for OpenBSD failed (or would have failed, had it been
run?) prior to that PR being issued.
(This was previously submitted as
https://github.com/acmesh-official/acmetest/pull/28 )
