Can't build uboot kernel

good morning, failing to build u-boot kernel from (https://github.com/radxa/rockchip-bsp)radxa/rockchip-bsp.

This is what the error returns
CHK include/generated/compile.h
SKIPPED include/generated/compile.h
MKIMAGE arch/arm64/boot/dts/rockchip/overlay/rockchip-fixup.scr
/bin/sh: 1: mkimage: not found
scripts/Makefile.lib:343: recipe for target ‘arch/arm64/boot/dts/rockchip/overlay/rockchip-fixup.scr’ failed
make[3]: *** [arch/arm64/boot/dts/rockchip/overlay/rockchip-fixup.scr] Error 127
scripts/Makefile.build:484: recipe for target ‘arch/arm64/boot/dts/rockchip/overlay’ failed
make[2]: *** [arch/arm64/boot/dts/rockchip/overlay] Error 2
scripts/Makefile.build:484: recipe for target ‘arch/arm64/boot/dts/rockchip’ failed
make[1]: *** [arch/arm64/boot/dts/rockchip] Error 2
arch/arm64/Makefile:127: recipe for target ‘dtbs’ failed
make: *** [dtbs] Error 2
make: *** Waiting for unfinished jobs…
CHK kernel/config_data.h
MAKE KERNEL IMAGE FAILED.