Instead of running mkdir from debian/rules, the native way to create the
necessary directories is with the dirs file which is read by the
dh_installdirs helper script.
See:
* https://www.debian.org/doc/manuals/maint-guide/dother.en.html#dirs
* dh_installdirs(1) manual page
I am not aware of any specific problems that could arise from doing it
manually instead of using dh_installdirs. But sticking to the native
approach might be a good idea.