Add test support for env to Makefile.
Add test support for env to Makefile.

dennis/coreutils,kwantam/coreutils,sshling/coreutils,steveklabnik/coreutils,Heather/coreutils,hexsel/coreutils,Shir0kamii/coreutils,silvio/rust-coreutils,dbrgn/coreutils,kevgeniy/coreutils,Heather/coreutils,bundai223/coreutils,Arcterus/coreutils,samfoo/coreutils,dennis/coreutils,hexsel/coreutils,keunwoo/coreutils,uutils/coreutils,uutils/coreutils,kevgeniy/coreutils,tempbottle/coreutils,retep998/coreutils,dbrgn/coreutils,kball/coreutils,Shtong/coreutils,steveklabnik/coreutils,samfoo/coreutils,keunwoo/coreutils,wimh/coreutils,silvio/rust-coreutils,uutils/coreutils,beni55/coreutils,sshling/coreutils,retep998/coreutils,ebfe/coreutils,filmor/coreutils,kwantam/coreutils,beni55/coreutils,efuquen/coreutils,filmor/coreutils,kball/coreutils,jbcrail/coreutils,mauricio/coreutils,Arcterus/coreutils,jbcrail/coreutils,Shir0kamii/coreutils,Gianbaoluo/coreutils,Shtong/coreutils,bundai223/coreutils,mauricio/coreutils,tempbottle/coreutils,ebfe/coreutils,dbrgn/coreutils,Gianbaoluo/coreutils,wimh/coreutils,efuquen/coreutils