Devil: prefer configured env over ANDROID_SDK_ROOT
Devil: prefer configured env over ANDROID_SDK_ROOT

The Devil library is currently configured to prefer the ANDROID_SDK_ROOT
environment variable over the hermetic Android SDK. This switches Devil
to prefer the hermetic SDK to make things more consistent across
machines.

The _LEGACY_ENVIRONMENT_VARIABLES logic was originally introduced by
Patchset #2 of https://codereview.chromium.org/1416703003/#ps20001,
however I can't determine the reason. A lot of time has passed since
then, so I'm hoping that chromium bots no longer rely on this behavior.

Bug: chromium:1348669
Test: I ran 'build/android/apk_operations.py' in my local checkout
Change-Id: I653cecac7ee108463ce69b635f3cbfbcc11cd09f
Reviewed-on: https://chromium-review.googlesource.com/c/catapult/+/3795007
Commit-Queue: Nate Fischer <72afde956856aeb0f00e5e8df797f0068a2ecaf8@chromium.org>
Reviewed-by: Ben Pastene <e214258550f76fa23ac7c1d953424f3f468f5c6b@chromium.org>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult