Generate API docs during build.

lib/dartdoc/dartdoc.dart

Index: lib/dartdoc/dartdoc.dart
diff --git a/lib/dartdoc/dartdoc.dart b/lib/dartdoc/dartdoc.dart
index fd8ecd12b666d9b1e20eef1cae122632d9b5d0e9..1f5a6293f20b5d67d9c3af8e86d139086e61c456 100644
--- a/lib/dartdoc/dartdoc.dart
+++ b/lib/dartdoc/dartdoc.dart
@@ -140,8 +140,9 @@ void cleanOutputDirectory(String path) {
   final outputDir = new Directory(path);
   if (outputDir.existsSync()) {
     outputDir.deleteRecursivelySync();
-    outputDir.createSync();
   }
+
+  outputDir.createSync();
 }
 
 /**
@@ -182,7 +183,7 @@ void compileScript(String compilerPath, String libDir,
   process.stdout.pipe(stdout, close: false);
 
   process.onError = (error) {
-    print('Failed to compile $dartPath. Error:');
+    print('Failed to compile $dartPath:');
     print(error);
   };
 }