tc: add support for make alongside kleaf

After the transition to kleaf for building the linux kernel and modules,
we lost support for building with make.

Linux 5.15 has official support for kleaf, (which uses Clang) but our
development branch which has some extra patches, does not support building
with Clang.

Because of this, building tc3-android13-linux5.15 will not work with
kleaf, so adding back support for make, which will be chosen as the
build system for linux versions lower than 6.1

Also moved cloning and patching gpu ddk under it's own build-gpu-ddk.sh
file, which is sourced where needed to avoid duplication, and keep the
same build flow.

Because make is generating the Image under LINUX_OUT/arch/arm64/boot and
kleaf is flattening all the outputs under LINUX_OUT, moved the Image
from kleaf under the same path as make.

Signed-off-by: Alex Dobrescu <alex.dobrescu@arm.com>