Fix build.

runtime/bin/main.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 
 #include "include/dart_api.h"
 #include "include/dart_tools_api.h"
@@ skipping 1427 matching lines @@
                      rodata_blob_size);
   } else {
     WriteSnapshotFile(snapshot_filename,
                       false,
                       assembly_buffer,
                       assembly_size);
   }
 }
 
 
+#if defined(TARGET_ARCH_X64)
 static void GeneratePrecompiledJITSnapshot() {
   uint8_t* vm_isolate_buffer = NULL;
   intptr_t vm_isolate_size = 0;
   uint8_t* isolate_buffer = NULL;
   intptr_t isolate_size = 0;
   uint8_t* instructions_blob_buffer = NULL;
   intptr_t instructions_blob_size = 0;
   uint8_t* rodata_blob_buffer = NULL;
   intptr_t rodata_blob_size = 0;
   Dart_Handle result = Dart_CreateAppJITSnapshot(
@@ skipping 11 matching lines @@
   WriteAppSnapshot(snapshot_filename,
                    vm_isolate_buffer,
                    vm_isolate_size,
                    isolate_buffer,
                    isolate_size,
                    instructions_blob_buffer,
                    instructions_blob_size,
                    rodata_blob_buffer,
                    rodata_blob_size);
 }
+#endif  // defined(TARGET_ARCH_X64)
 
 
 static void GenerateAppSnapshot() {
   Dart_Handle result;
 #if defined(TARGET_ARCH_X64)
   result = Dart_PrecompileJIT();
   if (Dart_IsError(result)) {
     ErrorExit(kErrorExitCode, "%s\n", Dart_GetError(result));
   }
   GeneratePrecompiledJITSnapshot();
@@ skipping 463 matching lines @@
   Platform::Exit(Process::GlobalExitCode());
 }
 
 }  // namespace bin
 }  // namespace dart
 
 int main(int argc, char** argv) {
   dart::bin::main(argc, argv);
   UNREACHABLE();
 }