Fix sky_tools build command to look for package-root in global args

packages/flutter_tools/lib/src/build.dart

@@ -150,7 +150,7 @@ class BuildCommand extends Command {
     await _compileSnapshot(
       compilerPath: argResults['compiler'],
       mainPath: argResults['main'],
-      packageRoot: argResults['package-root'],
+      packageRoot: globalResults['package-root'],
       snapshotPath: snapshotPath);
     archive.addFile(await _createSnapshotFile(snapshotPath));
 

packages/flutter_tools/lib/src/run_mojo.dart

@@ -27,7 +27,6 @@ class RunMojoCommand extends Command {
 
     argParser.addOption('app', defaultsTo: 'app.flx');
     argParser.addOption('mojo-path', help: 'Path to directory containing mojo_shell and services');
-    argParser.addOption('package-root', defaultsTo: 'packages');
   }
 
   Future<String> _makePathAbsolute(String relativePath) async {