revise RwLock for HermitCore#72954

Merged

bors merged 5 commits intorust-lang:masterfrom

hermit-os:rwlock

Jul 24, 2020

Commits on Jun 25, 2020

Commits on Jun 26, 2020

remove some compiler warnings
stlankes
committed

Commits on Jul 6, 2020

use latest version of hermit-abi
stlankes
committed