fix #27771, create directory if needed

pkg/dev_compiler/lib/src/compiler/compiler.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:collection' show HashSet, Queue;
 import 'dart:convert' show BASE64, JSON, UTF8;
 import 'dart:io' show File;
 import 'package:analyzer/dart/element/element.dart' show LibraryElement;
 import 'package:analyzer/analyzer.dart'
     show AnalysisError, CompilationUnit, ErrorSeverity;
@@ skipping 484 matching lines @@
       // In singleOutFile mode we wrap each module in an eval statement to
       // leverage sourceURL to improve the debugging experience when source maps
       // are not enabled.
       //
       // Note: We replace all `/` with `.` so that we don't break relative urls
       // to sources in the original sourcemap. The name of this file is bogus
       // anyways, so it has very little effect on things.
       c += '\n//# sourceURL=${name.replaceAll("/", ".")}.js\n';
       c = 'eval(${JSON.encode(c)});\n';
     }
-    new File(jsPath).writeAsStringSync(c);
+
+    var file = new File(jsPath);
+    if (!file.parent.existsSync()) file.parent.createSync(recursive: true);
+    file.writeAsStringSync(c);
+
     // TODO(jacobr): it is a bit strange we are writing the source map to a file
     // even when options.inlineSourceMap is true. To be consistent perhaps we
     // should also write a copy of the source file without a sourcemap even when
     // inlineSourceMap is true.
     if (code.sourceMap != null) {
-      new File(mapPath).writeAsStringSync(JSON.encode(code.sourceMap));
+      file = new File(mapPath);
+      if (!file.parent.existsSync()) file.parent.createSync(recursive: true);
+      file.writeAsStringSync(JSON.encode(code.sourceMap));
     }
   }
 }
 
 /// The output of compiling a JavaScript module in a particular format.
 class JSModuleCode {
   /// The JavaScript code for this module.
   ///
   /// If a [sourceMap] is available, this will include the `sourceMappingURL`
   /// comment at end of the file.
@@ skipping 24 matching lines @@
     // Fall back to a relative path.
     return path.toUri(path.relative(path.fromUri(uri), from: dir)).toString();
   }
 
   for (int i = 0; i < list.length; i++) {
     list[i] = transformUri(list[i]);
   }
   map['file'] = transformUri(map['file']);
   return map;
 }