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

subprocess.cc

 // Copyright (c) 2009 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/subprocess.h"
 #include <stdlib.h>
 #include <string.h>
 #include <string>
 #include <unistd.h>
 #include <vector>
@@ skipping 144 matching lines @@
     return false;
   }
   ScopedFreeArgPointer argp_free(argp);
 
   char* child_stdout;
 
   bool success = g_spawn_sync(
       NULL,  // working directory
       argv.get(),
       argp,
-      static_cast<GSpawnFlags>(G_SPAWN_STDERR_TO_DEV_NULL | flags),  // flags
+      static_cast<GSpawnFlags>(G_SPAWN_STDERR_TO_DEV_NULL |
+                               G_SPAWN_SEARCH_PATH | flags),  // flags
       GRedirectStderrToStdout,  // child setup function
       NULL,  // data for child setup function
       &child_stdout,
       NULL,
       return_code,
       &err);
   FreeArgv(argv.get());
   if (err)
     LOG(INFO) << "err is: " << err->code << ", " << err->message;
   if (child_stdout && strlen(child_stdout))
     LOG(INFO) << "Subprocess output:\n" << child_stdout;
   return success;
 }
 
 Subprocess* Subprocess::subprocess_singleton_ = NULL;
 
 }  // namespace chromeos_update_engine