rat plugin fails in mult-iproject build when subproject has surefire-plugin forkCount=0

We have a project using the apache-rat-plugin:0.12 to verify licenses, and it suddenly started failing with a FileNotFoundException for a subproject file that certainly does exist. I have attached the output from the maven build and build with -X as build-ouput.rtf and build-outputX.rtf respectively.

One can go into the tck subproject and run the build and rat has no problem processing the file from within that directory.

After reversing changes to find what the cause was, it came down to the tck/pom.xml use of forkCount=0 in the maven-surefire-plugin configuration. I have know idea why this should affect the rat plugin, but it does.

To reproduce the issue:

1. git clone https://github.com/eclipse/microprofile-jwt-auth.git
2. git checkout tags/ratbug
3. mvn clean install

Changing the forkCount to 1 or higher fixes the FileNotFound problem.