[beta] std: Synchronize access to global env during `exec`#55978

Merged

bors merged 2 commits intorust-lang:betafrom alexcrichton:beta-next

Nov 15, 2018

+83-106

Commits on Nov 15, 2018

Revert "Fixes rust-lang#46775 -- don't mutate the process's environment in Command::exec"
alexcrichton
committed
std: Synchronize access to global env during exec

alexcrichton
and
alex
committed