
This roughly restores the order of operation from Spack 0.20, where where `AutotoolsPackage.setup_build_environment` would override the env variable set in `setup_platform_environment` on macOS.
This roughly restores the order of operation from Spack 0.20, where where `AutotoolsPackage.setup_build_environment` would override the env variable set in `setup_platform_environment` on macOS.