CentOS 8.x에서 std::span 사용

1. gcc-toolset 설치
   yum install gcc-toolset-10
   (10버전 이상부터 std::span이 사용가능)

2. scl source 등록
   source scl_source enable gcc-toolset-10

3-1. scl 설정 bash 적용
scl enable gcc-toolset-10 bash
scl run gcc-toolset-10 bash

3-2. visual studio cross platform 적용
In the Configuration Properties -> C/C++ -> General -> C/C++ Compiler
both the C Compiler and the C++ Compiler values from just "g++" to the full path /opt/rh/gcc-toolset-10/root/bin/g++

4. c++20 옵션 적용
   g++ ... -std=c++2a