Add -f -r flags to find-unused-errs
Add -f -r flags to find-unused-errs

Reviewed-by: Andy Polyakov <015edf36635e030d5e009e08808a59984e629740@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3230)
openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl