Suppress warning in Flatbuffer VS2010 builds.

Change-Id: I4f66a96ba581704c1a384cc700b8fb731d3eeed4
diff --git a/CMakeLists.txt b/CMakeLists.txt
index affa05b..23a96b8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -145,7 +145,8 @@
 
 elseif(MSVC)
   # Visual Studio pedantic build settings
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4 /WX")
+  # warning C4512: assignment operator could not be generated
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4 /WX /wd4512")
 endif()
 
 if(FLATBUFFERS_CODE_COVERAGE)