Moved Discord RPC library's source code to external

Source/UnitTests/UnitTests.vcxproj

@@ -45,7 +45,7 @@
         The following libs are needed since we pull in pretty much the entire
         dolphin codebase.
         -->
-      <AdditionalLibraryDirectories>$(ExternalsDir)ffmpeg\lib;$(ExternalsDir)discord-rpc\lib;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
+      <AdditionalLibraryDirectories>$(ExternalsDir)ffmpeg\lib;$(IntDir)..\discord-rpc\bin;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
       <AdditionalDependencies>avrt.lib;iphlpapi.lib;winmm.lib;setupapi.lib;opengl32.lib;glu32.lib;rpcrt4.lib;comctl32.lib;avcodec.lib;avformat.lib;avutil.lib;swresample.lib;swscale.lib;Shlwapi.lib;discord-rpc.lib;%(AdditionalDependencies)</AdditionalDependencies>
       <SubSystem>Console</SubSystem>
     </Link>