Well, as is usually the case, as soon as I'm convinced I'm stuck and send off a note, I try something else and make a bit
of progress......sigh.  The new project I was trying to integrate with an ecm usb network device interface had the following in prj.conf:

CONFIG_NEWLIB_LIBC=y

As soon as I removed that line, nrfx_usbd.c compiled - as did everything else.  The requirement for newlib may have been historical
and possibly irrelevant now.  I was doing some testing with a 3rd party source code package.  But, I don't know if this constitutes an
issue with the newlib code in the present distribution (1_13_99).  Can't say that my code is now functional, but the bizarre compiler behavior has disappeared. 
So, I think an interaction with the current newlib code is the cause of my initial problem.

Any comments on this are appreciated.  I may need newlib for compatibility reasons later on....would like to understand what's going on
here.

Regards,
Chuck McP