Use sizeof() instead of strlen().

mrbgems/mruby-bin-debugger/tools/mrdb/apilist.c

@@ -45,7 +45,7 @@ build_path(mrb_state *mrb, const char *dir, const char *base)
   len = strlen(base) + 1;
 
   if (strcmp(dir, ".")) {
-    len += strlen(dir) + strlen("/");
+    len += strlen(dir) + sizeof("/") - 1;
   }
 
   path = mrb_malloc(mrb, len);

mrbgems/mruby-bin-debugger/tools/mrdb/mrdb.c

@@ -275,7 +275,7 @@ get_command(mrb_state *mrb, mrdb_state *mrdb)
   if (i == 0 && feof(stdin)) {
     clearerr(stdin);
     strcpy(mrdb->command, "quit");
-    i += strlen("quit");
+    i += sizeof("quit") - 1;
   }
 
   if (i == MAX_COMMAND_LINE) {