JaCoCo for Graal

Graal uses JaCoCo for coverage reports.

Since Graal lives in the bootclasspath, we need a patch to JaCoCo. The jacocoagent binaries that are downloaded by mx are thus custom builds that contain this patch.
The original patch that was used is here and was used to make the jacocoagent.jar/jacocoagent-original.jar binaries.
A new version of this patch can be found in this pull request. It was used to build jacocoagent-0.7.1-1.jar. Note that as mentioned in this pull request, a better version of this patch exists and should be included in JaCoCo 0.7.2.

The source code of the JaCoCo HTML reporter used in Graal can be found in this repository.