I've used XCode4 for a large C++ project. The project uses make for build. I've set up XCode4 to use external build tool make so that my Makefile is called each time I hit build and I see compile errors nicely within XCode.
First, this worked OK but recently XCode4 crashes a lot. Now I am switching back to XCode3 but I cannot find out how to set up build using an external build tool in XCode 3.2.5.
I'm not sure if this is what you are looking for, but when I'm ready to build an external static framework I use a bunch of scripts I have written and you can see at my Github repo. Look in the scripts directory and at the build.sh which configures and calls them.
I've used these scripts on both XCode 3 and XCode 4. They make use of xcodebuild and a couple of external tools such as appledoc and produces a distributable (versioned) DMG file if successful.
You can use these scripts if you like or just take a look to see how they work and get ideas for your own.