This fixes building D8 when SCons cannot figure the build environment and it is passed using the env argument. This is usually only used when building with Visual Studio 2008.
Review URL: http://codereview.chromium.org/542009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3574 ce2b1a6d-e550-0410-aec6-3dcde31c8c00