Fix explicit arrays with non-constant size for -fc-prototypes.

gcc/fortran/ChangeLog:

	PR fortran/120139
	* dump-parse-tree.cc (get_c_type_name): If no constant
	size of an array exists, output an asterisk.

Author: Thomas Koenig

gcc/fortran/dump-parse-tree.cc

@@ -4371,6 +4371,8 @@ get_c_type_name (gfc_typespec *ts, gfc_array_spec *as, const char **pre,
 	  mpz_clear (sz);
 	  *asterisk = false;
 	}
+      else
+	*asterisk = true;
     }
   return ret;
 }