Bug 120544 [build path] Editing external source folder does not persist
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/BuildPathsBlock.java
IResource res= entry.getResource();
				if (res instanceof IFolder) {
					if (entry.getLinkTarget() != null) {
						IFolder folder= ((IFolder)res);
						if (!res.exists()) {
							folder.createLink(entry.getLinkTarget(), IResource.ALLOW_MISSING_LOCAL, monitor);
						} else if (!entry.getLinkTarget().equals(res.getLocation())) {
							folder.delete(true, monitor);
							folder.createLink(entry.getLinkTarget(), IResource.ALLOW_MISSING_LOCAL, monitor);
						}
					} else if (!res.exists()) {
						CoreUtility.createFolder((IFolder)res, true, true, null);
					}
				}
				if (entry.getEntryKind() == IClasspathEntry.CPE_SOURCE) {
					IPath folderOutput= (IPath) entry.getAttribute(CPListElement.OUTPUT);
					if (folderOutput != null && folderOutput.segmentCount() > 1) {
						IFolder folder= fWorkspaceRoot.getFolder(folderOutput);
						CoreUtility.createFolder(folder, true, true, null);
					}
					
					IPath path= entry.getPath();
					if (projPath.equals(path)) {
						monitor.worked(1);
						continue;	
					}
					
					if (projPath.isPrefixOf(path)) {
						path= path.removeFirstSegments(projPath.segmentCount());