build: Add chromium prebuilt support to envsetup.sh && The core Makefile

This adds a chromium_prebuilt function to envsetup.sh that is invoked by lunch to check
whether the chromium prebuilts are up-to-date or not. If not, it will be built from source
and then the new source built version will be pulled during brunch/mka bacon to become the
new prebuilts for future builds.

This is all opt-in through the USE_PREBUILT_CHROMIUM flag. Without it being set to 1,
none of this would be ran, and regular operations will go on.

PS13:
-use export TARGET_DEVICE
-replace git -C with params compatible to old git versions

(vendor repository for script)

Change-Id: I40f8c8dbd2a8a84a5c1b9f47ee04180a71ef4e07

Conflicts:
	core/Makefile
Prebuilt chromium: Run a check for target device directory

this should fix the issue that arises if device fails and device is built again,
chromium will error out because it thinks the prebuilt files exist (which they are
not, directories are just created).

Signed-off-by: Ayysir <ayysir@aospal.com>
Change-Id: I595cab268e66c738ccae9900150b36d7f9626a6e
Prebuilt chromium: update for lollipop

Change-Id: I4e34feb26c1b4bec10fb751a10dbc52579d7cd07
add package complete

Change-Id: I8eccd682fa203cdb152db34583faebe8a4491ea7
remove prebuilt apk check

Change-Id: I39d22ba403a013a1be2f80d73860c0544315ef69
core/main.mk: Allow OpenJDK

OpenJDK is an equivilent implementation of java and
will produce the same results as oracle JDK

Change-Id: I4da51ce9bbd1988777a2d887605482852609c6ba
Signed-off-by: Evan Anderson <evananderson@aospa.co>
core: Allow to disable block based OTA's

on Xiaomi Mi2, it causes that the user can't install GAPPS because
the filesystem is smaller than the partition then(users resize the syspart).

Change-Id: I1dcde9c9a212c34108629537cb8c1088a0373573