Comment 0 for bug 1931580

On Hirsute v5.4 the ubuntu_bpf fail to build with:

  make[1]: Leaving directory '/home/azure/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf'
  make: Leaving directory '/home/azure/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests'
  stderr:
  Warning: Kernel ABI header at 'tools/include/uapi/linux/netlink.h' differs from latest version at 'include/uapi/linux/netlink.h'
  Warning: Kernel ABI header at 'tools/include/uapi/linux/if_link.h' differs from latest version at 'include/uapi/linux/if_link.h'
  Makefile:45: *** "rst2man not found, but required to generate man pages". Stop.
  make[1]: *** [Makefile:188: /home/azure/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/tools/sbin/bpftool] Error 2
  make[1]: *** Deleting file '/home/azure/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/tools/sbin/bpftool'
  make: *** [Makefile:165: all] Error 2