Merge pull request #9305 from r-burns/discord

Exclude Discord RPC lib from installation

CMakeLists.txt

@@ -794,7 +794,7 @@ endif()
 
 if(USE_DISCORD_PRESENCE)
   message(STATUS "Using static DiscordRPC from Externals")
-  add_subdirectory(Externals/discord-rpc)
+  add_subdirectory(Externals/discord-rpc EXCLUDE_FROM_ALL)
   include_directories(Externals/discord-rpc/include)
 endif()