Change to download and build zlib every time, in case a bot happens to die during a build

Change-Id: I04e3bfcf520eef8b7fe41cfa1cb04e87de413363
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2052585
Commit-Queue: Amy Huang <akhuang@google.com>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#750365}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: c7fc84754ca04cfc4b733e56bf7a383653eaa8a6
1 file changed