simplify the bazel-provider to use a search path appraoch

pkg/compiler/bin/resolver.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:io';
 
 import 'package:args/args.dart';
 import 'package:compiler/src/apiimpl.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/null_compiler_output.dart';
 import 'package:compiler/src/options.dart';
 import 'package:compiler/src/serialization/json_serializer.dart';
 import 'package:compiler/src/source_file_provider.dart';
 import 'package:package_config/discovery.dart';
 
 main(var argv) async {
   var parser = new ArgParser();
   parser.addOption('deps', abbr: 'd', allowMultiple: true);
   parser.addOption('out', abbr: 'o');
   parser.addOption('library-root', abbr: 'l');
   parser.addOption('packages', abbr: 'p');
-  parser.addOption('bazel-config');
+  parser.addOption('bazel-paths', abbr: 'I', allowMultiple: true);
   var args = parser.parse(argv);
 
   var resolutionInputs = args['deps']
       .map((uri) => currentDirectory.resolve(nativeToUriPath(uri)))
       .toList();
   var root = args['library-root'];
   var libraryRoot = root == null
       ? Platform.script.resolve('../../../sdk/')
       : currentDirectory.resolve(nativeToUriPath(root));
 
   var options = new CompilerOptions(
       libraryRoot: libraryRoot,
       packageConfig: args['packages'] == null
           ? null
           : currentDirectory.resolve(args['packages']),
       resolveOnly: true,
       resolutionInputs: resolutionInputs,
       packagesDiscoveryProvider: findPackages);
 
-  var bazelConfigPath = args['bazel-config'];
-  var inputProvider = bazelConfigPath != null
-      ? new BazelInputProvider(bazelConfigPath)
+  var bazelSearchPaths = args['bazel-paths'];
+  var inputProvider = bazelSearchPaths != null
+      ? new BazelInputProvider(bazelSearchPaths)
       : new CompilerSourceFileProvider();
 
   var outputProvider = const NullCompilerOutput();
   var diagnostics = new FormattingDiagnosticHandler(inputProvider);
   var compiler =
       new CompilerImpl(inputProvider, outputProvider, diagnostics, options);
 
   if (args.rest.isEmpty) {
     print('missing input files');
     exit(1);
@@ skipping 21 matching lines @@
       inputs.map((lib) => compiler.libraryLoader.lookupLibrary(lib)).toList();
 
   var serializer =
       compiler.serialization.createSerializer(librariesToSerialize);
   var text = serializer.toText(const JsonSerializationEncoder());
 
   var outFile = args['out'] ?? 'out.data';
 
   await new File(outFile).writeAsString(text);
 }