Add a profile to enable compilation with javac

[laeubi]

Sometimes there is a question "does it compile with javac" and doing so by hand can become cumbersome.

This now adds a new profile "javac" that can be used to enable javac as a compiler instead of ecj and disable baseline compare/replace because of javac emits different bytecode by default.

[iloveeclipse]

@laeubi : for non-maven users, could you provide maven commands to use (for both SDK aggregator and for a single project)?

[laeubi]

Build failure is unrelated.

@iloveeclipse for any usual build simply add -Pjavac e.g. if you checkout p2 you can run

mvn clean install -Pjavac -DskipTests

[akurtakov]

It wouldn't hurt to have this one to make testing easier.

[iloveeclipse]

Have you seen that the code doesn't compil, but it doesn't compile in a different place?
Why that? Is the compilation order not stable?

https://ci.eclipse.org/platform/job/eclipse.platform.releng.aggregator/job/PR-2983/2/console

16:40:46  [ERROR] Failed to execute goal org.eclipse.tycho:tycho-compiler-plugin:4.0.13-SNAPSHOT:compile (default-compile) on project org.eclipse.jface.databinding: Compilation failure: Compilation failure: 
16:40:46  [ERROR] /home/jenkins/agent/workspace/atform.releng.aggregator_PR-2983/eclipse.platform.ui/bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/viewers/ViewerSupport.java:[79] 
16:40:46  [ERROR] 	Properties.observeEach(contentProvider.getKnownElements(), labelProperties)));
16:40:46  [ERROR] 	           ^^^^^^^^^^^
16:40:46  [ERROR] The method observeEach(IObservableSet<E>, IValueProperty<? super E,? extends P>...) in the type Properties is not applicable for the arguments (IObservableSet<E>, IValueProperty<? super E,?>[])
16:40:46  [ERROR] /home/jenkins/agent/workspace/atform.releng.aggregator_PR-2983/eclipse.platform.ui/bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/viewers/ViewerSupport.java:[123] 
16:40:46  [ERROR] 	Properties.observeEach(contentProvider.getKnownElements(), labelProperties)));
16:40:46  [ERROR] 	           ^^^^^^^^^^^
16:40:46  [ERROR] The method observeEach(IObservableSet<E>, IValueProperty<? super E,? extends P>...) in the type Properties is not applicable for the arguments (IObservableSet<E>, IValueProperty<? super E,?>[])
16:40:46  [ERROR] /home/jenkins/agent/workspace/atform.releng.aggregator_PR-2983/eclipse.platform.ui/bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/viewers/ViewerSupport.java:[175] 
16:40:46  [ERROR] 	Properties.observeEach(contentProvider.getKnownElements(), labelProperties)));
16:40:46  [ERROR] 	           ^^^^^^^^^^^
16:40:46  [ERROR] The method observeEach(IObservableSet<E>, IValueProperty<? super E,? extends P>...) in the type Properties is not applicable for the arguments (IObservableSet<capture#22-of ? extends E>, IValueProperty<? super E,?>[])
16:40:46  [ERROR] /home/jenkins/agent/workspace/atform.releng.aggregator_PR-2983/eclipse.platform.ui/bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/viewers/ViewerSupport.java:[230] 
16:40:46  [ERROR] 	Properties.observeEach(contentProvider.getKnownElements(), labelProperties)));
16:40:46  [ERROR] 	           ^^^^^^^^^^^
16:40:46  [ERROR] The method observeEach(IObservableSet<E>, IValueProperty<? super E,? extends P>...) in the type Properties is not applicable for the arguments (IObservableSet<capture#34-of ? extends E>, IValueProperty<? super E,?>[])
16:40:46  [ERROR] 4 problems (4 errors)
16:40:46  [ERROR] -> [Help 1]

[laeubi]

That is the same failure as before my change (see master build), the Jenkins job uses parallel execution, as that it might compile in different order depending on how many CPU time is there.

So I think this shows not only P2 is affected.

[laeubi]

Here is also a CI job using that new profile:

• https://github.com/eclipse-equinox/p2/actions/runs/14360386397/job/40260075212?pr=786

it currently fails to upload the event-file twice, but the jobs itself are running....