make uImage

  OBJCOPY arch/arm/boot/Image
  Kernel: arch/arm/boot/Image is ready
  AS      arch/arm/boot/compressed/head.o
  GZIP    arch/arm/boot/compressed/piggy.gz
  AS      arch/arm/boot/compressed/piggy.o
  CC      arch/arm/boot/compressed/misc.o
  LD      arch/arm/boot/compressed/vmlinux
  OBJCOPY arch/arm/boot/zImage
  Kernel: arch/arm/boot/zImage is ready
  UIMAGE  arch/arm/boot/uImage
"mkimage" command not found - U-Boot images will not be built
  Image arch/arm/boot/uImage is ready
找不到mkimage 工具，
问题解决：将uboot源码目录中tools中mkimage工具拷贝到系统目录/usr/bin/中