GCC/Linux: missing return type to error

CMakeLists.txt

@@ -162,7 +162,7 @@ if (WIN32) # TODO(nick) Should do based upon compiler (VS)
 	set(OS_LIBS "")
 else()
 	add_definitions(-DUNIX)
-	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17 -msse3")
+	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17 -msse3 -Werror=return-type")
 	set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -D_DEBUG -pg -Wall")
 	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3 -mfpmath=sse")
 	set(OS_LIBS "dl")