Gradle task jalviewjsTranspile does not fail on eclipse error

During the jalviewjs build process in gradle, the jalviewjsTranspile task uses an external eclipse (usually installed in ~/buildtools/eclipse) to run the transpilation.

Sometimes, for unknown reasons, this installation can get itself into a state that runs, but does not run the transpilations, even though it has the j2s plugin present (and running). In this case the jalviewjsTranspile task doesn't fail although it has not transpiled any jalview classes.

The jalviewjsTranspile task can analyse the eclipse output to decide whether a suitably successful transpilation has happened.

In future, it may be that the jalviewjsTranspile task runs eclipse but eclipse decides nothing is new to compile and therefore nothing is compiled or transpiled so try and take account of that.