japiCmp Gradle task does not have a relocatable build cache

[jprinet]

If you run the JapiCmp task from 2 different folders with the same inputs, you can't benefit from Gradle build cache as one of the input (richReport.rules's Map) is using an absolute path as value.

In my cache relocation experience, the cost was 33 tasks executed in 33 projects totaling 39.212s building micronaut-core:
./gradlew clean check -x :http-server-netty:test

[melix]

I'm actually not quite sure how to fix this properly. At least, I don't think this can be done properly simply by changing the micronaut-build project: the rules probably need to be able to use a MapProperty instead of just a Map, which requires changes to the japicmp plugin. Even if they do so, the value would still be a String...

[jprinet]

I was wondering if "just" using a relative path could help.
That would be a simpler change but I'm unsure of the implications / feasibility