github workflow should use the various java versions to test,
which permits to test especially 2d rendering differences.
the javac release flag is set to produce java8 binaries in
any case. not perfect, but we only loose a warning that
applets are to be removed after java17, trivial to display
by adding the javac release property, when using java17:
mvn --batch-mode compile -Dmaven.compiler.release=17
gradle clean build -x javaDoc -PjavacRelease=17
better would be to separate build and test, as suggested
by https://github.com/matthew16550, here:
https://github.com/plantuml/plantuml/pull/904
it runs on all platforms with java-17, but the javac release flag
is set to 8, 11, and 17 respectively. artifact upload happens
from latest ubuntu LTS, 20.04, java-8.
workflow and scripts are duplicated so nothing existing breaks.
ci-gradle triggers are commented apart from the workflow trigger
which allows manual start, so one can compare artifacts.
