Generate API docs during build.

lib/dartdoc/dartdoc.dart

 // Copyright (c) 2012, 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.
 
 /**
  * To generate docs for a library, run this script with the path to an
  * entrypoint .dart file, like:
  *
  *     $ dart dartdoc.dart foo.dart
  *
@@ skipping 122 matching lines @@
   return dirname(new File(new Options().script).fullPathSync());
 }
 
 /**
  * Deletes and recreates the output directory at [path] if it exists.
  */
 void cleanOutputDirectory(String path) {
   final outputDir = new Directory(path);
   if (outputDir.existsSync()) {
     outputDir.deleteRecursivelySync();
-    outputDir.createSync();
   }
+
+  outputDir.createSync();
 }
 
 /**
  * Copies all of the files in the directory [from] to [to]. Does *not*
  * recursively copy subdirectories.
  *
  * Note: runs asynchronously, so you won't see any files copied until after the
  * event loop has had a chance to pump (i.e. after `main()` has returned).
  */
 void copyFiles(String from, String to) {
@@ skipping 1122 matching lines @@
 
     return new md.Element.text('code', name);
   }
 
   // TODO(rnystrom): Move into SourceSpan?
   int getSpanColumn(SourceSpan span) {
     final line = span.file.getLine(span.start);
     return span.file.getColumn(line, span.start);
   }
 }