When running skip test, we sometimes see failures like:

[✗] …/SkipTestHarness/XCSkipTests.swift:10: error: -[XCSkipTests testSkipModule] : failed - The file “skipapp-hiya” couldn’t be saved in the folder “build” because a file with the same name already exists.

Re-running the tests almost always results in them passing. The speculated cause is because skip test runs tests in parallel, multiple builds might be simultaneously be trying to create a symlink to the same destination when they see it doesn't exist.

This PR tolerates failed attempts to create the symlink, provided that the symlink is pointing to the expected destination.