wget http://ftp.libre-soc.org/rootfs.cpio
CROSS_COMPILE="ccache powerpc64le-linux-gnu-" ARCH=powerpc make -j8 O=microwatt microwatt_defconfig
CROSS_COMPILE="ccache powerpc64le-linux-gnu-" ARCH=powerpc make -j8 O=microwatt
This will produce a file
microwatt/arch/powerpc/boot/dtbImage.microwatt
wget http://ftp.libre-soc.org/rootfs.cpio
CROSS_COMPILE="ccache powerpc64le-linux-gnu-" ARCH=powerpc make -j8 O=microwatt microwatt_defconfig
CROSS_COMPILE="ccache powerpc64le-linux-gnu-" ARCH=powerpc make -j8 O=microwatt
This will produce a file
microwatt/arch/powerpc/boot/dtbImage.microwatt