How to compile stuff against the official AOSP source repo?

Sorry if this has been asked/answered before, but the search terms i can think of are too vague, and come up with results on how to compile the repo itself, or a kernel, etc etc.

After setting up my build environment for android, and pulling the repo with 'repo sync', and building it, how would one compile, say, GNU binutils or busybox for android? More specifically, how do i tell the armv7 cross-compiler/linker to link against libs found in the repo tree? (preferably using command line tools, and not "all-in-one" IDE's or graphical front-ends)

Thanks for any help!