manta: Set TARGET_ARCH_VARIANT to cortex-a15

Change-Id: Iea43e322f8aa374ea69fc90f9d84a4c2c4c78750
manta: Set TARGET_ARCH_VARIANT to cortex-a15

Change-Id: Iea43e322f8aa374ea69fc90f9d84a4c2c4c78750
manta: Enable WebGL

Change-Id: Iada49f1ea604182835753a48ba8dc115b86ff18d