Fixing CMakeLists.txt for older Cmake
See
@@ -2,6 +2,9 @@ cmake_minimum_required(VERSION 3.9)
project(VulkanMemoryAllocator)
+# https://cmake.org/cmake/help/latest/variable/PROJECT_IS_TOP_LEVEL.html
+string(COMPARE EQUAL ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_SOURCE_DIR} PROJECT_IS_TOP_LEVEL)
+
if(PROJECT_IS_TOP_LEVEL)
find_package(Vulkan REQUIRED)
endif()
