Change precedence of options in bazel.
Change precedence of options in bazel.

Now options specified in BUILD files can override defaults.

Change-Id: I88586805b2f4dffd18d3920efbede906f670cdf0

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed