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
if (oldOutputLocation.equals(projPath) && !outputLocation.equals(projPath)) {
				if (BuildPathsBlock.hasClassfiles(project)) {
					if (BuildPathsBlock.getRemoveOldBinariesQuery(JavaPlugin.getActiveWorkbenchShell()).doQuery(projPath)) {
						BuildPathsBlock.removeOldClassfiles(project);
					}
				}
			}
			
			IWorkspaceRoot fWorkspaceRoot= JavaPlugin.getWorkspace().getRoot();
			
			
			if (!fWorkspaceRoot.exists(outputLocation)) {
				IFolder folder= fWorkspaceRoot.getFolder(outputLocation);
				CoreUtility.createFolder(folder, true, true, null);
				folder.setDerived(true);		
			}
			
			if (monitor.isCanceled()) {
				throw new OperationCanceledException();
			}
			monitor.worked(2);
			
			int nEntries= classPathEntries.size();
			IClasspathEntry[] classpath= new IClasspathEntry[nEntries];
			int i= 0;
			
			for (Iterator iter= classPathEntries.iterator(); iter.hasNext();) {
				CPListElement entry= (CPListElement)iter.next();
				classpath[i]= entry.getClasspathEntry();
				i++;