This makes C++11 a requirement and prevents a "decay" to C++98 when the compiler does not support C++11.
set(CMAKE_CXX_STANDARD_REQUIRED ON)
This disables the use of compiler-specific extensions.
For example, by default, CMake passes -std=gnu++11to GCC on Linux. We want to build with -std=c++11 to prevent use of non-portable compiler extensions, which is what the disabling of this option does.
https://github.com/samstyle/Xpeccy/blob/15c7cadbb271e99a0123e7d1b72726a8e02d35fb/CMakeLists.txt#L2
cmake_minimum_required(VERSION 3.14...3.19 FATAL_ERROR)Enable C++11
set(CMAKE_CXX_STANDARD 11)This makes C++11 a requirement and prevents a "decay" to C++98 when the compiler does not support C++11.
set(CMAKE_CXX_STANDARD_REQUIRED ON)This disables the use of compiler-specific extensions.
set(CMAKE_CXX_EXTENSIONS OFF)Allow multi core usage
set(CMAKE_BUILD_PARALLEL_LEVEL)