Only depend on icudata on windows.

On windows, this triggers the dll to be copied to the correct
locations. On other platforms, icudata is compiled in, and depending on
it results in an invalid linker archive ordering.

BUG=v8:2745
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/18734003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15619 ce2b1a6d-e550-0410-aec6-3dcde31c8c00