fix warning: getenv not secure

Just silence the warning. Yes, the Right Thing to do would be to use the newer and safer ways instead of getenv, but silencing it is simpler and suffices for this project's needs :)

CMakeLists.txt

@@ -33,6 +33,7 @@ message(STATUS "Found ASSIMP in ${ASSIMP_INCLUDE_DIR}")
 
 if(WIN32)
   set(LIBS glfw3 opengl32 assimp freetype irrKlang)
+  add_definitions(-D_CRT_SECURE_NO_WARNINGS)
 elseif(UNIX AND NOT APPLE)
   set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Wall")
   find_package(OpenGL REQUIRED)