Add accidentally deleted 'if /x64' line back

BUG=440500

Review URL: https://codereview.chromium.org/1663753004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298580 0039d316-1c4b-4281-b951-d872f2087c98

win_toolchain/package_from_installed.py

@@ -216,7 +216,8 @@ def GenerateSetEnvCmd(target_dir):
       f.write('%~dp0..\\..\\win_sdk\\Include\\WINVERSION\\ucrt;'.replace(
                   'WINVERSION', WIN_VERSION))
     f.write('%~dp0..\\..\\VC\\include;'
-            '%~dp0..\\..\\VC\\atlmfc\\include\n')
+            '%~dp0..\\..\\VC\\atlmfc\\include\n'
+            'if "%1"=="/x64" goto x64\n')
 
     # x86. Always use amd64_x86 cross, not x86 on x86.
     f.write('set PATH=%~dp0..\\..\\win_sdk\\bin\\x86;'