CHROMIUMOS: Finalize placeholder Makefile for ebuild compatibility. Copy common.mk locally BUG=none TEST=build using this Makefile, see build product works. Change-Id: I27916cec7c85d5c15513451a016e622e74035dd0 Signed-off-by: Terry Lambert <[email protected]> Reviewed-on: https://gerrit.chromium.org/gerrit/26494 Reviewed-by: Mike Frysinger <[email protected]>