ir-merges.txt breaks build cache when trackSourceFiles enabled

[midery]

In Gradle, AbstractKotlinCompile.incremental parameter considered as a compile task input, and if this value is changed, we cannot reuse previously saved cache entry:

Task ':delegate:sample:app:compileDebugKotlin' is not up-to-date because:
Value of input property 'incrementalCompilationEnabled$kotlin_gradle_plugin_common' has changed for task ':delegate:sample:app:compileDebugKotlin'
The input changes require a full rebuild for incremental task ':delegate:sample:app:compileDebugKotlin'.

This becomes a problem when we use remote caches:

• In our CI, we run cache warmup job on a clean repository without any build folders, thus ir-merges.txt does not exist there, and the incremental compilation turned on.
• Locally, developers always have the build folders saved to their project, and ir-merges.txt exists in them, so the incremental compilation turned off.

So when we try to reuse remote cache on a local machine, it does not get reused:

Reproducible scenario without remote cache:

1. Turn on trackSourceFiles option in Anvil extension
2. Run gradle clean
3. Run gradle delegate:sample:app:assembleDebug
4. Do any change in a file in :sample:app module. Example: rename MyActivity to MyActivity2.
5. Run gradle delegate:delegate:sample:app:assembleDebug --no-build-cache, so we will have build directory updated, but caches store the old value.
6. Revert the change from Step 4 (we're at the exactly same position as we were in Step 3, only difference is our build folder is not clean.
7. Run gradle :sample:app:assembleDebug
8. In logs, you see that the delegate:sample:app:compileDebugKotlin was not taken from cache, but was re-executed.

Introduced in: 2.5.0-beta11.