[NaCl SDK] Enable linux host build for nacl_io and nacl_io_tests.

native_client_sdk/src/libraries/nacl_io/kernel_handle.cc

 // Copyright (c) 2012 The Chromium 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 "nacl_io/kernel_handle.h"
 
 #include <errno.h>
 #include <pthread.h>
 
 #include "nacl_io/mount.h"
@@ skipping 37 matching lines @@
     if (error)
       return error;
   }
 
   return 0;
 }
 
 Error KernelHandle::Seek(off_t offset, int whence, off_t* out_offset) {
   // By default, don't move the offset.
   *out_offset = offset;
-  size_t base;
+  ssize_t base;
   size_t node_size;
 
   AUTO_LOCK(handle_lock_);
   Error error = node_->GetSize(&node_size);
   if (error)
     return error;
 
   switch (whence) {
-    default:
-      return -1;
     case SEEK_SET:
       base = 0;
       break;
     case SEEK_CUR:
       base = handle_attr_.offs;
       break;
     case SEEK_END:
       base = node_size;
       break;
+    default:
+      return -1;
   }
 
   if (base + offset < 0)
     return EINVAL;
 
-  off_t new_offset = base + offset;
+  size_t new_offset = base + offset;
 
   // Seeking past the end of the file will zero out the space between the old
   // end and the new end.
   if (new_offset > node_size) {
     error = node_->FTruncate(new_offset);
     if (error)
       return EINVAL;
   }
 
   *out_offset = handle_attr_.offs = new_offset;
@@ skipping 132 matching lines @@
     return ENOTSOCK;
   if (OpenMode() == O_RDONLY)
     return EACCES;
 
   AUTO_LOCK(handle_lock_);
   return sock->SendTo(handle_attr_, buf, len, flags, dest_addr, addrlen,
                       out_len);
 }
 
 }  // namespace nacl_io