add support for ancient cmake

CMakeLists.txt

@@ -7,11 +7,11 @@ add_compile_options(-std=c++17 -Wall -Wextra -Wpedantic -Wno-unused-parameter)
 if(CMAKE_BUILD_TYPE STREQUAL Debug OR CMAKE_BUILD_TYPE STREQUAL "")
 	message(STATUS "Build mode: Debug")
 	add_compile_options(-g -fsanitize=address)
-	add_link_options(-fsanitize=address)
+	set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -fsanitize=address")
 elseif(CMAKE_BUILD_TYPE STREQUAL Release)
 	message(STATUS "Build mode: Release")
 	add_compile_options(-O3 -flto)
-	add_link_options(-flto)
+	set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -flto")
 else()
 	message(FATAL_ERROR "CMAKE_BUILD_TYPE must be Debug or Release.")
 endif()