build-kernel.sh: Support 'arm64' architecture.

This patch adds support for --arch=arm64 to the build-kernel.sh
script. Note that this requires android-goldfish-3.10 or higher,
and is currently limited to the 'defconfig' default config.

This is enough to build an AARCH64 kernel, but there is no guarantee
at this point that it can run under either QEMU or the Android emulator.

Change-Id: Idc3ecc3e3b9b8f06aeba9c4710903f55c64331df
1 file changed