Add USE_X11 flag to turn off lid_touchpad_helper

We'll do something different on the ozone/freon board variants,
since there's no X server to interact with.

BUG=chromium:397311
TEST=build & install on link_freon with USE=-X
CQ-DEPEND=CL:209616

Change-Id: I2b4a060370e16eb772e762a889372c64a7830693
Reviewed-on: https://chromium-review.googlesource.com/209573
Reviewed-by: Albert Chaulk <achaulk@chromium.org>
Commit-Queue: Michael Spang <spang@chromium.org>
Tested-by: Michael Spang <spang@chromium.org>
1 file changed