AU: locate bsdiff/bspatch in $PATH, rather than hard coding their location.

delta_diff_generator.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "update_engine/delta_diff_generator.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
 #include <sys/stat.h>
@@ skipping 1614 matching lines @@
   }
 
   int64_t manifest_metadata_size =
       strlen(kDeltaMagic) + 2 * sizeof(uint64_t) + serialized_manifest.size();
   ReportPayloadUsage(manifest, manifest_metadata_size, op_name_map);
 
   LOG(INFO) << "All done. Successfully created delta file.";
   return true;
 }
 
-const char* const kBsdiffPath = "/usr/bin/bsdiff";
-const char* const kBspatchPath = "/usr/bin/bspatch";
+const char* const kBsdiffPath = "bsdiff";
+const char* const kBspatchPath = "bspatch";
 const char* const kDeltaMagic = "CrAU";
 
 };  // namespace chromeos_update_engine