strip_package: Update to style guide.

Convert strip_package to respect the style guide.
In particular, use argparse instead of optparse.

BUG=None
TEST=`cros lint`
TEST=`strip_package --board=gizmo libchromeos` works.

Change-Id: I0dd528f468238e97d4679b66dc8af2fc44cb51ee
Reviewed-on: https://chromium-review.googlesource.com/268677
Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
1 file changed