common-mk: Remove the arc variable

This is the cleanup step for
https://chromium-review.googlesource.com/#/c/372921/ .

CQ-DEPEND=CL:365122,CL:376921
BUG=b:30230518
TEST=emerge chromeos-base/chromeos-login

Change-Id: Ic25ec5a378d2c18cc2b42de86b2d8868d25da185
Reviewed-on: https://chromium-review.googlesource.com/376845
Commit-Ready: Luis Hector Chavez <lhchavez@google.com>
Tested-by: Luis Hector Chavez <lhchavez@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed