We should somehow disable the partially-installed SDK or at least print an error when sourcing the env setup script, because several people now have had the SDK installation fail and yet they've missed the failure message and then wondered why things don't work in the installed SDK.
Fix merged to master: http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=28a2ea701c97bd2d68a211af3aedb4d70ae7852c