我是嵌入式Linux系统的初学者，并尝试构建crosstool-NG版本1.20.0 但是我收到如下错误消息：
[INFO ] Performing some trivial sanity checks
[INFO ] Build started 20190429.203109
[INFO ] Building environment variables
[WARN ] Directory '/home/superwheel/src' does not exist.
[WARN ] Will not save downloaded tarballs to local storage.
[EXTRA] Preparing working directories
[EXTRA] Installing user-supplied crosstool-NG configuration
[EXTRA] =================================================================
[EXTRA] Dumping internal crosstool-NG configuration
[EXTRA] Building a toolchain for:
[EXTRA] build = x86_64-unknown-linux-gnu
[EXTRA] host = x86_64-unknown-linux-gnu
[EXTRA] target = arm-cortex_a8-linux-gnueabi
[EXTRA] Dumping internal crosstool-NG configuration: done in 0.03s (at 00:01)
[INFO ] =================================================================
[INFO ] Retrieving needed toolchain components' tarballs
[EXTRA] Retrieving 'linux-3.15.4'
[ERROR]
[ERROR] >>
[ERROR] >> Build failed in step 'Retrieving needed toolchain components' tarballs'
[ERROR] >> called in step '(top-level)'
[ERROR] >>
[ERROR] >> Error happened in: do_kernel_get[scripts/build/kernel/linux.sh@741]
[ERROR] >> called from: main[scripts/crosstool-NG.sh@582]
[ERROR] >>
[ERROR] >> For more info on this error, look at the file: 'build.log'
[ERROR] >> There is a list of known issues, some with workarounds, in:
[ERROR] >> 'docs/B - Known issues.txt'
[ERROR]
[ERROR] (elapsed: 0:01.53)
[00:02] / ct-ng:148: recipe for target 'build' failed
make: *** [build] Error 1
我的主机：Ubuntu 16.04，x86_64 GCC / G ++版本：5.5.0
也许有人可以向我建议其他跨工具链？谢谢