Fix benign compiler warning in logging macro

The strncpy intentionally is not copying the NULL terminator for the log
message prefix. The NULL will be added by vsnprintf, after.
Switching to memcpy eliminates the warning.

libclamav/others_common.c

@@ -142,7 +142,7 @@ void cl_set_clcb_msg(clcb_msg callback)
     va_list args;                                         \
     size_t len = sizeof(x) - 1;                           \
     char buff[MSGBUFSIZ];                                 \
-    strncpy(buff, x, len);                                \
+    memcpy(buff, x, len);                                 \
     va_start(args, str);                                  \
     vsnprintf(buff + len, sizeof(buff) - len, str, args); \
     va_end(args)