darwin: Fix screenshot

Issue: https://github.com/741g/android-emulator-m1-preview/issues/6

Since we switched to main thread posting only, we didn't account for the
screenshot command.

Cherry-pick aosp/1524438

Test: Screenshot works (x86, M1)

Change-Id: I745bcaa7c18df3fab07c59b7cfdbccf093d300ad
4 files changed
tree: 2771a84eb8cf704e4048edbcfbcf45acffe0c531
  1. base/
  2. host-common/
  3. snapshot/