[tlbuild] Testing

[Karl Berry]

    Context and LuaTeX both failed because of missing format files; they  
    tried to create these fmt files but failed. I assume mktexfmt doesn't  
    yet make their format files.

Context is completely different from everything else and makes its own
format files when it feels like it.  No format files should be
attempted, except for mptopdf.  Is that what you're talking about?

I haven't committed the luatex format stuff yet, so I don't understand
why it's trying to do those either.