Squash chromium prebuilt feature (2/2)

Credits to OmniROM and PA

vendor/omni: Add chromium_prebuilt.sh

This script will pull the necessary libs from a complete build and generate proper
makefiles in order to support using a prebuilt Chromium. Files are placed in
prebuilts/chromium/-devicenamehere-, and are not tracked by git, so they are completely
out of the way.

PS3:
-replace git -C with params compatible to old git versions

Change-Id: I3141defcbd4108178881f7203f3105aecc27378b

Prebuilt chromium: update script for lollipop

Change-Id: I3fbef0d23e76a6f5c25579d1ca9336bcfe19290d

Conflicts:
	utils/chromium_prebuilt.sh

Run chromium_prebuilt.mk if feature is enabled

Change-Id: I87090170a6972b3b96827e81ef3e6509eb376f93
Finisher script (2/2)

Change-Id: I20363713a827629294ffe71f92ebd2d0001026e3