Use the provided image build variables to point the kernel-bin build
command to the kernel we are interested in.
Signed-off-by: Mathias Kresin <dev@kresin.me>
This new subtarget sets the small_flash flag and removes unused kernel
configuration.
small_flash removes KERNEL_KALLSYMS, which saves ~107KB in the default
configuration; removing unneeded hardware support from ar71xx/tiny saves
another ~18KB (both after LZMA).
Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>