Kernel: add new variables for TARGET_KERNEL_CUSTOM_LINARO_TOOLCHAIN

(cherry picked from commit 615d67ed3bd2b8ae4511d8d021681ae705fa8be5)
Signed-off-by: Hieu Phan <aznrice2k4@gmail.com>

Conflicts:
	core/tasks/kernel.mk

Change-Id: Ic824ec172f38c9cb27f6fb6ed3e6efd1705cf976