你好，我在编译Uboot时候遇到了一个错误，请问是什么问题？log 如下：
......
CC lib/linux_string.o
CC lib/membuff.o
CC lib/slre.o
CC lib/string.o
CC lib/tables_csum.o
CC lib/time.o
CC lib/uuid.o
CC lib/vsprintf.o
CC lib/panic.o
CC lib/strto.o
CC lib/strmhz.o
LD lib/built-in.o
CC net/checksum.o
CC net/arp.o
CC net/bootp.o
CC net/eth-uclass.o
CC net/eth_common.o
CC net/net.o
CC net/nfs.o
CC net/ping.o
CC net/tftp.o
LD net/built-in.o
LD test/built-in.o
CC test/dm/cmd_dm.o
LD test/dm/built-in.o
CC examples/standalone/stubs.o
LD examples/standalone/libstubs.o
CC examples/standalone/hello_world.o
LD examples/standalone/hello_world
OBJCOPY examples/standalone/hello_world.srec
OBJCOPY examples/standalone/hello_world.bin
LDS u-boot.lds
LD u-boot
OBJCOPY u-boot-nodtb.bin
../scripts/dtc-version.sh: line 17: dtc: command not found
../scripts/dtc-version.sh: line 18: dtc: command not found
*** Your dtc is too old, please upgrade to dtc 1.4 or newer
make[1]: *** [checkdtc] Error 1
make[1]: Leaving directory `/home/songzhen/RockTech_Project/Linux_project/AM335X-SDK/board-support/u-boot-2017.01+gitAUTOINC+590c7d7fe1-g590c7d7fe1/am335x_evm'
make: *** [sub-make] Error 2
