I have tried to reproduce here - but it just works.
I then took a second look at your excellent bug-report and noticed:
that in this commandline you say M=PWD
which tell kbuild that module is in a directory named 'PWD' as seen in the
assignment to KBUILD_EXTMOD in the above line.
Could it be that you by accident omitted a '$' in front of PWD?
This would then tell kbuild that module are in the directory pointed to by $PWD.
Sam
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