devel/kronosnet: Unbreak build with GCC 9

In file included from common.c:22:
In function 'open_lib',

inlined from 'load_module' at common.c:130:11:

logging.h:21:17: error: '%s' directive argument is null [-Werror=format-overflow=]

21 | #define LOG_MSG log_msg
   |                 ^

logging.h:30:2: note: in expansion of macro 'LOG_MSG'

30 |  LOG_MSG(knet_h, subsys, KNET_LOG_WARN, fmt, ##args)
   |  ^~~~~~~

common.c:85:3: note: in expansion of macro 'log_warn'

85 |   log_warn(knet_h, KNET_SUB_COMMON, "unable to dlinfo %s: %s",
   |   ^~~~~~~~

common.c: In function 'load_module':
common.c:85:59: note: format string is defined here

85 |   log_warn(knet_h, KNET_SUB_COMMON, "unable to dlinfo %s: %s",
   |

PR: 238330
Obtained from: upstream