Enable parallel build in Release MSVC

Add /MP flag for Release since we're not using incremental rebuild. 
This should make compilation faster

Source/CMakeLists.txt

@@ -93,7 +93,7 @@ if(MSVC)
 	endif()
 	
 	set(CMAKE_CXX_FLAGS_OPTIMIZEDDEBUG "${BS_COMPILER_FLAGS_COMMON} /GL /Gy /Zi /Gm /O2 /Oi /MD")
-	set(CMAKE_CXX_FLAGS_RELEASE "${BS_COMPILER_FLAGS_COMMON} /GL /Gy /O2 /Oi /MD")
+	set(CMAKE_CXX_FLAGS_RELEASE "${BS_COMPILER_FLAGS_COMMON} /GL /Gy /O2 /Oi /MD /MP")
 	
 	# Global defines
 	add_definitions(-D_HAS_EXCEPTIONS=0)