remove install plan from build scripts

Remove the flags for saving the emerge install plan from build scripts.
Saving this incorrect data to an intermediate file is no longer
necessary since the new reverse dependency calculation code is already
submitted.

BUG=chromium:864309
TEST=local builds and tryjobs
CQ-DEPEND=CL:1190424

Change-Id: I405400bbdef0d8c88b4877eb1fab38dea5af8217
Reviewed-on: https://chromium-review.googlesource.com/1191762
Commit-Ready: Gregory Meinke <gmeinke@chromium.org>
Tested-by: Gregory Meinke <gmeinke@chromium.org>
Reviewed-by: Gregory Meinke <gmeinke@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
3 files changed