[madgraph2021 v0.7, MR 649] merge qa-build-mg5amc-madgraph4gpu commit a3e86d0e from 4388927

Changed the title to mention "[madgraph2021 v0.7, MR 649]"

This merges into master the changes for mg2021 and infrastructure in !649 (merged) (where madgraph2021 v0.7 was built)