strip_package: source common.sh directly

We're no longer installing this.

BUG=None
TEST=CQ passed

Change-Id: I7a3906763e13e65374c26bb462bbe74b14d0b939
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/1856661
Reviewed-by: Amin Hassani <[email protected]>
Tested-by: Mike Frysinger <[email protected]>
1 file changed