Manifest: Add Many Custom Kernel Toolchains

* Options now include TARGET_GCC_VERSION_ARM := 4.7-linaro 4.7-sm 4.8-linaro 4.8-sm 4.9-sm 4.10-sm
* Note: Only use one option at a time. TARGET_GCC_VERSION_ARM := belongs in your BoardConfig.mk

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