I'm not sure what exactly to do about that. Your best bet should be to just keep on using Xcode 3. Xcode 4 doesn't do much for this project, really.
If that fails, you should contact Apple support to figure out how to resolve this. My bet would be to get the release version of Xcode 4 (because that's what I have). You can find it on the App Store. But I can't guarantee that that fixes things; I don't know how the installer handles the nonstandard installation directory. Either it writes over Xcode 3 and stuff works, like it does on my box, or it writes into your /Xcode 4/ folder and the situation's still the same. I can't tell from here.
You might be able to resolve this also by making a backup of /Developer/ and copying the files from /Xcode 4/ into place, but again, there's no guarantee.
To get an idea what the differences are between the folders, open a terminal and type something like
Code: Select all
ls -m /Xcode\ 4/*
Code: Select all
ls -m /Developer/*
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Can you currently compile sample projects featuring OpenGL elements with your preview Xcode 4 installation? Because if you can, then the Lugaru project should principally be adjustable to account for nonstandard locations of headers and stuff. I'd test that first and then we'll go from there.