core: Fix unextractable translation string

Glib format specifiers are not gettext friendly. It even emits a
warning: src/core/main-utils.c:196: warning: Although being used in a
format string position, the msgid is not a valid C format string."

One possible solution is to use the equivalent format specifiers from
<inttypes.h> like PRId64, available since C99.

Even simpler is to cast the value to a type that is big enough to hold
it according to C specs (i.e. for int64: long long).

Fixes: 50f34217f9 ('main: use _nm_utils_ascii_str_to_int64 instead of strtol for reading pid')

src/core/main-utils.c

@@ -192,10 +192,7 @@ nm_main_utils_ensure_not_running_pidfile(const char *pidfile)
     if (strcmp(process_name, prgname) == 0) {
         /* Check that the process exists */
         if (kill(pid, 0) == 0) {
-            fprintf(stderr,
+            fprintf(stderr, _("%s is already running (pid %lld)\n"), prgname, (long long) pid);
-                    _("%s is already running (pid %" G_GINT64_FORMAT ")\n"),
-                    prgname,
-                    (gint64) pid);
             exit(1);
         }
     }