Arc Land freezing on windows

Reproduction Instructions
be on windows, attempt to land an accepted diff, after having gotten rid of the call to nonblocking stdin on line 97 of arcanistprompt (because otherwise that throws an exception) – you’ll get to the ‘land this diff, y/n/?’, pressing y causes an indefinite hang

Phabricator/Arcanist Version
arcanist 92f860ae9b2fc0b2c50061f1f6bba6bf04af5f8c (10 Jun 2020)

the commit that breaks it is https://github.com/phacility/arcanist/commit/68f28a1718887eb386d97b452a679a950d48a70e

See https://discourse.phabricator-community.org/t/arc-land-fail-unable-to-set-stdin-nonblocking/4006/.