Hmm - looks like PIX is a typedef in the "leptonica" project. Even though I installed leptonica, the opendias build is not able to find it.
Leptonica is apparently needed for OCR. OK, I can do without OCR to try things out. So I found the two uses of the PIX in import_doc.c,
and bracketed them with "#ifdef CAN_OCR", and got a complete build.