Track Custom Kernel Toolchains

* Many legacy devices don't support 4.8 and many of the newer devices do
better on 4.9-4.10 so this just makes sense. Same flag as KitKat Liquid.

Signed-off-by: Chet Kener <Cl3Kener@gmail.com>
Change-Id: I0026a1d3ae5d432db10150d1a15f7cb8e7a6054b
Signed-off-by: Chet Kener <Cl3Kener@gmail.com>