handle overloaded virtual warnings as error using Clang

CMakeLists.txt

@@ -65,11 +65,14 @@ if ( ${CMAKE_CXX_COMPILER_ID} STREQUAL "Intel" )
     endif ()
 
 elseif (${CMAKE_CXX_COMPILER_ID} MATCHES "Clang")
-    add_compile_options (-Werror -Wsign-compare -Wunused-variable -Warray-bounds)
+    add_compile_options (-Werror)
+    add_compile_options (-Wsign-compare)
+    add_compile_options (-Wunused-variable)
+    add_compile_options (-Warray-bounds)
     # Increase template depth for boost
     add_compile_options (-ftemplate-depth=1024)
     # Allow overloaded virtual functions (instances to be fixed in OPAL)
-    add_compile_options (-Wno-overloaded-virtual)
+    #add_compile_options (-Wno-overloaded-virtual)
     add_definitions(-DIPPL_RESTRICT_BUG)
     if (ENABLE_OpenMP)
 	    add_compile_options (-fopenmp)