Otherwise, setting udev_log=debug in /etc/udev/udev.conf has no effects since
systemd-udevd is built with LOG_REALM=LOG_REALM_UDEV.
However using LOG_REALM_UDEV (for libudev_core) reveals another similar bug for
udevadm which should also define LOG_REALM_UDEV.
#
# exe = executable('udevadm',
# udevadm_sources,
+# c_args : ['-DLOG_REALM=LOG_REALM_UDEV'],
# include_directories : includes,
# link_with : [libudev_core,
# libsystemd_network,