ANDROID: build config for cuttlefish ramdisk

Both x86 and arm64 are covered in this change.
The ramdisk and ko's are put in the DIST_DIR by the
BUILD_INITRAMFS option.

Bug: 139431025
Test: Local build and boot of cf
Signed-off-by: Ram Muthiah <rammuthiah@google.com>
Change-Id: I82a410ea3cf9b9177a1c8f2186d88344b9a63488