RSN 8 - Change minimum support gcc/g++ version to 9.x

Author	RAPIDS Ops
Status	Completed
Topic	Platform Support Change
RAPIDS Version	v0.20 / v21.06
Created	April 29, 2021
Updated	May 5, 2021

Overview

All RAPIDS projects will require gcc/g++ 9.0+ in order to take advantage of new C++ features, notably including moving to C++17.

This also aligns RAPIDS with the current conda-forge build stack.

Status

All conda builds and docker images use gcc/g++ 9.3 starting with v0.20 (now v21.06).

Impact

Users building from source should use gcc/g++ 9.0 or higher to build RAPIDS.