cmake_minimum_required(VERSION 3.5) if (${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR}) message(FATAL_ERROR "In-source builds not allowed. Please make a new directory (called a build directory) and run CMake from there. You may need to remove CMakeCache.txt." ) endif() if(TARGET system) # Guard for use as transitive dependency return() endif() # Project project(system) set(CMAKE_CXX_STANDARD 11) add_subdirectory(system)