Is there an existing issue for this?

• I have searched the existing infra issues

Type of Request

bug

Infrastructure Environment

Recipes

What is happening?

In recipes, when the Xcode cache is cleared, we unmount all runtimes. Afterward, we will reinstall and remount the needed runtimes. Before remounting, though, we check to see if it need to be remounted.

It seems that the command to unmount runtimes (xcrun simctl runtime delete all) does not wait for it complete, which may cause issues like the example below:

For example: https://ci.chromium.org/ui/p/flutter/builders/try/Mac%20Engine%20Drone/477518/overview
In step 20.2, the runtimes are unmounted
In step 21.2, we can see the unmounted hasn't finished though because the runtimes are still available
Also, there are no verify and mount runtime substeps in 21, which means it thought the runtimes were still mounted (https://flutter.googlesource.com/recipes/+/refs/heads/main/recipe_modules/osx_sdk/api.py#340)

Steps to reproduce

Unfortunately this does not happen every time since it's a race condition

Expected results

I expect runtimes to be remounted if applicable after unmounting.