remove references to DART_SDK from editor

editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/internal/builder/BuildDartParticipant.java

 /*
  * Copyright (c) 2012, the Dart project authors.
  * 
  * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
  * 
  * http://www.eclipse.org/legal/epl-v10.html
  * 
  * Unless required by applicable law or agreed to in writing, software distributed under the License
  * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
@@ skipping 299 matching lines @@
 
     // If we have a snapshot, use that.
     if (snapshotCompiler != null && snapshotCompiler.getDestFile().exists()) {
       args.add(snapshotCompiler.getDestFile().getPath());
     } else {
       args.add(builderFile.getName());
     }
 
     args.addAll(buildArgs);
 
+    //TODO (danrubel): Older build.dart may rely on DART_SDK env var... so leave for now
     Map<String, String> env = builder.environment();
     DartSdk sdk = DartSdkManager.getManager().getSdk();
     env.put("DART_SDK", sdk.getDirectory().getAbsolutePath());
 
     builder.command(args);
     builder.directory(container.getLocation().toFile());
     builder.redirectErrorStream(true);
 
     ProcessRunner runner = new ProcessRunner(builder);
 
@@ skipping 250 matching lines @@
   /**
    * @return whether we should invoke any build.dart files in the given project
    */
   private boolean shouldRunAnyBuildDart(IProject project) {
     boolean disableBuilder = DartCore.getPlugin().getDisableDartBasedBuilder(project);
 
     return !disableBuilder;
   }
 
 }