The status-file flags and the flags from the test case's source code
must always overwrite extra flags set by bots.

Bug: v8:6924
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I0e2aabb69da7cfb8ba6c1c79bd3851462071a6ac
Reviewed-on: https://chromium-review.googlesource.com/732656
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49001}