how to cause unix 'make' to know how many times to run *tex

I've used in the past this Makefile, from Yannick Copin.

But, I guess latexmk also has some advantage over make (although I like using custom Makefile).

You also get an undefined reference, when it is an unknown one ...

You can delete the time stamp line from the logfile and then build the md5 sum or whatever. When it didn't change then you have no changes in the document. You can also speedup your compilation time, when you do not build a pdf in the first or two run: pdflatex -draftmode ..., then only the aux|idx|...-files will be created to get correct labels/references.

See latexmake and UltimateLatexMakefile for instance. See also Tools for automating document compilation.