This is QT version 3 and we cannot move up right now. I am the first in our group to use openGL within the QT environment. The qmake procedure puts this option in the Makefile:
It only does this when the following has been added to the dot pro file:
I found a link here: https://www.x.org/releases/X11R7.7/doc/libXmu/Xmu.html
for Xmu and XMUU library API Reference where the introduction begins with:
We don’t have this package and of several hundred apps none need it. So here is the question:
Is there any way to modify qmake such that it will not add this option?

No. If QMake adds it, it's because Qt itself needs it.

In this example said option was edited out of Makefile and the project successfully built and ran. That is pretty good evidence that it is not always needed. I don't have a clue as to what causes it to be required. QT is used extensively and our build process detects the need to run qmake, runs it, then runs the resultant make. I suppose we could add some scripting code that hunts down option -lXmu and removes it. It would be far better to eliminate it at the source rather than to patch it up.

OTOH: We might add a new file in with each application and list the options that are to be removed. From offhand comments we might then be able to remove some software that really is not needed but added just because QT or some other package demands it. Still, it would be better to stop them before being generated rather than hunt them down later.