Change to X64 default build in tool scripts in sdk/bin

sdk/bin/dart2js.bat

 @echo off
 REM Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 REM for details. All rights reserved. Use of this source code is governed by a
 REM BSD-style license that can be found in the LICENSE file.
 
 setlocal
 rem Handle the case where dart-sdk/bin has been symlinked to.
 set DIR_NAME_WITH_SLASH=%~dp0
 set DIR_NAME=%DIR_NAME_WITH_SLASH:~0,-1%%
 call :follow_links "%DIR_NAME%", RETURNED_BIN_DIR
@@ skipping 21 matching lines @@
 )
 
 rem Get absolute full name for DART_ROOT.
 for %%i in ("%SDK_DIR%\..\") do set DART_ROOT=%%~fi
 
 rem Remove trailing backslash if there is one
 if %DART_ROOT:~-1%==\ set DART_ROOT=%DART_ROOT:~0,-1%
 
 set DART2JS=%DART_ROOT%\pkg\compiler\lib\src\dart2js.dart
 
-rem DART_CONFIGURATION defaults to ReleaseIA32
-if "%DART_CONFIGURATION%"=="" set DART_CONFIGURATION=ReleaseIA32
+rem DART_CONFIGURATION defaults to ReleaseX64
+if "%DART_CONFIGURATION%"=="" set DART_CONFIGURATION=ReleaseX64
 
 set BUILD_DIR=%DART_ROOT%\build\%DART_CONFIGURATION%
 
 set PACKAGE_ROOT=%BUILD_DIR%\packages
 
 "%DART%" %EXTRA_VM_OPTIONS% "--package-root=%PACKAGE_ROOT%" "%DART2JS%" %EXTRA_OPTIONS% %*
 
 endlocal
 
 exit /b %errorlevel%
 
 :follow_links
 setlocal
 for %%i in (%1) do set result=%%~fi
 set current=
 for /f "usebackq tokens=2 delims=[]" %%i in (`dir /a:l "%~dp1" 2^>nul ^
                                              ^| find ">     %~n1 ["`) do (
   set current=%%i
 )
 if not "%current%"=="" call :follow_links "%current%", result
 endlocal & set %~2=%result%
 goto :eof
 
 :end