Fix Unity build in non Windows environment.

Author: yfakariya

test/MsgPack.UnitTest.Unity.Il2cpp.Full.Desktop/MsgPack.UnitTest.Unity.Il2cpp.Full.Desktop.csproj

@@ -789,9 +789,10 @@
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <PropertyGroup>
-    <PostBuildEvent>RoboCopy $(ProjectDir)$(OutDir) $(ProjectDir)\..\MsgPack.UnitTest.Unity.Il2cpp.Full\Assets\Plugins\Dlls\ *.dll /MIR
+    <PostBuildEvent Condition="'$(OS)' == 'Windows_NT'">RoboCopy $(ProjectDir)$(OutDir) $(ProjectDir)\..\MsgPack.UnitTest.Unity.Il2cpp.Full\Assets\Plugins\Dlls\ *.dll /MIR
 if %25ERRORLEVEL%25 geq 8 exit 1
 exit 0</PostBuildEvent>
+    <PostBuildEvent Condition="'$(OS)' != 'Windows_NT'">rsync -a -r --delete $(ProjectDir)$(OutDir)/*.dll $(ProjectDir)/../MsgPack.UnitTest.Unity.Il2cpp.Full/Assets/Plugins/Dlls/</PostBuildEvent>
   </PropertyGroup>
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.