Add initial libfuzzers for fm2js transpiling and XML parsing.

build/all.gyp

 # Copyright 2014 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     {
       'target_name': 'All',
       'type': 'none',
       'dependencies': [
         '../pdfium.gyp:*',
         '../samples/samples.gyp:*',
+        '../testing/libfuzzer/fuzzers.gyp:*',
       ],
     }
   ]
-}
+}