buildroot构建根文件系统报错是什么原因

buildroot构建根文件系统报错：
xtyc@ubuntu:~/work/buildroot-2019.02.9$ sudo make
>>> toolchain-external-custom  Configuring
Unable to detect the toolchain sysroot, Buildroot cannot use this toolchain.
package/pkg-generic.mk:228: recipe for target '/home/xtyc/work/buildroot-2019.02.9/output/build/toolchain-external-custom/.stamp_configured' failed
make: *** [/home/xtyc/work/buildroot-2019.02.9/output/build/toolchain-external-custom/.stamp_configured] Error 1
xtyc@ubuntu:~/work/buildroot-2019.02.9$

提示错误：Unable to detect the toolchain sysroot, Buildroot cannot use this toolchain.
有知道原因的吗？