kunit compile failed on um

[Cixi Geng]

Hi Brendan:
When I run kunit test in um , it failed on kernel 5.8-rc* while
succeeded  in v5.7 with same configuration. is this a bug?

Here is my operation:
 gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)

the kunitconfig:
Cixi.Geng:~/git-projects/torvals-linux$ cat .kunitconfig
CONFIG_KUNIT=y
CONFIG_KUNIT_TEST=y
CONFIG_KUNIT_EXAMPLE_TEST=y

command:
Cixi.Geng:~/git-projects/torvals-linux$ ./tools/testing/kunit/kunit.py run

the Error log:
[17:51:14] Configuring KUnit Kernel ...
[17:51:14] Building KUnit Kernel ...
ERROR:root:b"make[1]:
\xe8\xbf\x9b\xe5\x85\xa5\xe7\x9b\xae\xe5\xbd\x95\xe2\x80\x9c/home/cixi.geng1/git-projects/torvals-linux/.kunit\xe2\x80\x9d\n/home/cixi.geng1/git-projects/torvals-linux/Makefile:551:
recipe for target 'outputmakefile' failed\nmake[1]:
\xe7\xa6\xbb\xe5\xbc\x80\xe7\x9b\xae\xe5\xbd\x95\xe2\x80\x9c/home/cixi.geng1/git-projects/torvals-linux/.kunit\xe2\x80\x9d\nMakefile:185:
recipe for target '__sub-make' failed\n"