Bug 37197 Basepath for relative pathes in JAR-exporter
The basepath for the JAR-exporter is the eclipse-install-directory. I prefer it to be the root of the project (the description is saved in), so that relative pathes end inside the project. Now: <jardesc> <jar path="workspace/projectdir/jar.jar"/> Desired: <jardesc> <jar path="jar.jar"/> Reason: To make the jardesc-files portable for shared projects
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarFileExportOperation.java
if (realEx instanceof ZipException && realEx.getMessage() != null && realEx.getMessage().startsWith("duplicate entry:")) 
					addWarning(ex.getMessage(), realEx);
				else
					addToStatus(ex);
			}
		}					
	}
	private boolean isOutputFolder(IFolder folder) {
		try {
			IJavaProject javaProject= JavaCore.create(folder.getProject());
			IPath outputFolderPath= javaProject.getOutputLocation();
			return folder.getFullPath().equals(outputFolderPath);
		} catch (JavaModelException ex) {
			return false;
		}
	}
	private void exportClassFiles(IProgressMonitor progressMonitor, IPackageFragmentRoot pkgRoot, IResource resource, IJavaProject jProject, IPath destinationPath) {
		if (fJarPackage.areClassFilesExported() && isJavaFile(resource) && pkgRoot != null) {
			try {
				if (!jProject.isOnClasspath(resource))
					return;
				
				Iterator iter= filesOnClasspath((IFile)resource, destinationPath, jProject, pkgRoot, progressMonitor);
				IPath baseDestinationPath= destinationPath.removeLastSegments(1);
				while (iter.hasNext()) {
					IFile file= (IFile)iter.next();
					if (!resource.isLocal(IResource.DEPTH_ZERO))						
						file.setLocal(true , IResource.DEPTH_ZERO, progressMonitor);
					IPath classFilePath= baseDestinationPath.append(file.getName());
					progressMonitor.subTask(JarPackagerMessages.getFormattedString("JarFileExportOperation.exporting", classFilePath.toString()));