Merge pull request #5540 from nuttycom/feature/wallet_unified_addresses-fix_osx_build

Fix missing std::variant header that was breaking Darwin builds.

src/zcash/address/unified.h

@@ -10,6 +10,8 @@
 #include "script/script.h"
 #include "zip32.h"
 
+#include <variant>
+
 namespace libzcash {
 
 // prototypes for the classes handling ZIP-316 encoding (in Address.hpp)