add link-time optimization for release builds

CMakeLists.txt

@@ -34,6 +34,8 @@ if(CMAKE_COMPILER_IS_GNUCC OR "${CMAKE_C_COMPILER_ID}" STREQUAL "Clang")
         set(CMAKE_C_LINK_FLAGS "${CMAKE_C_LINK_FLAGS} -Wl,-z,norelro -Wl,--hash-style=gnu -Wl,--build-id=none")
 	endif()
     if(CMAKE_BUILD_TYPE STREQUAL "MinSizeRel" OR CMAKE_BUILD_TYPE STREQUAL "Release")
+        add_definitions(-flto)
+        set(CMAKE_C_LINK_FLAGS "${CMAKE_C_LINK_FLAGS} -flto")
         set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -s") # strip binary
     endif()
 endif()