ir-merges.txt causes configuration cache invalidation on next build

[joshfriend]

Example error: Calculating task graph as configuration cache cannot be reused because the file system entry '../out/android-register_samples_account-screen-sample_login-screen_demo/build/anvil/debug/caches/ir-merges.txt' has been created.

1. clear configuration cache
2. clean the build
3. run a build with configuration cache enabled
4. rerun the same build without making any changes, you'll see the above message

Seems to have been introduced in 87a85a2 (#1024)