Ignore .cxx/ directories

[stuartmorgan-g]

Android builds now create .cxx directories in some cases; this has been added to the app template's ignore file, so should be ignored here as well. As is generally the case for this repo, we ignore it at the root level instead of updating every package.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

[stuartmorgan-g]

test-exempt: configuration change

[auto-submit]

autosubmit label was removed for flutter/packages/9268, because - The status or check suite Linux_web web_platform_tests_shard_3 stable has failed. Please fix the issues identified (or deflake) before re-applying this label.