Automate building reports using Docker and SDKMAN

[pivovarit]

The process of setting up the environment for the sake of generating a report was in my case a bit tedious so I automated and encapsulated all of that in a single Dockerfile - making it possible to generate reports without downloading multiple JDKs and messing up with Maven's toolchains.xml.

Parameter names (especially JDKs) remained unchanged and might seem just wrong (just as the JDK version of the builder) - wanted to make the change minimally invasive so I adapted to the existing shape of the codebase.

At the end of the build, the jdk-api-diff.html spawns in a directory from which the command was called.

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In order to build an example report between SDKMAN distributions tagged 11.0.5-open and 12.0.2-open, run:

./compare.sh 11.0.5-open 12.0.2-open

which becomes effectively:

docker build --build-arg JDK1=11.0.5-open --build-arg JDK2=12.0.2-open -t jdk-api-diff .
docker run --rm --entrypoint cat jdk-api-diff target/jdk-api-diff.html > ./jdk-api-diff.html

If you don't know what available distributions are, run the script without providing build-args:

./compare.sh

or just:

docker build -t jdk-api-diff .

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Depends on: https://github.com/AdoptOpenJDK/jdk-api-diff/pull/8 ✅

[karianna]

@gunnarmorling Should we proceed with this PR?

[pivovarit]

After such a long time... it's probably not working anymore. But I'm willing to update it if needed.