https://bugs.gentoo.org/924019
(same as https://bugs.gentoo.org/914583 given rapidjson is bundled)

https://github.com/Tencent/rapidjson/issues/718
https://github.com/Tencent/rapidjson/commit/3b2441b87f99ab65f37b141a7b548ebadb607b96
From: Janusz Chorko <janusz.chorko@apdu.pl>
Date: Fri, 26 Aug 2016 21:17:38 +0200
Subject: [PATCH] Removed non-compiling assignment operator. Fixed #718
--- a/src/third-party/discord-rpc/include/rapidjson/document.h
+++ b/src/third-party/discord-rpc/include/rapidjson/document.h
@@ -317,6 +317,4 @@
     GenericStringRef(const GenericStringRef& rhs) : s(rhs.s), length(rhs.length) {}
 
-    GenericStringRef& operator=(const GenericStringRef& rhs) { s = rhs.s; length = rhs.length; }
-
     //! implicit conversion to plain CharType pointer
     operator const Ch *() const { return s; }