Cannot .configure WindowMaker 0.95.8 - Xmu lib issues

[James Geering]

Hi All,
I have just moved from RedHat and have progressed with the learning
curve
of moving to FreeBSD. I'm running 11.1-release #0 r321309 amd64.
I have installed Xorg and am running WindowMaker 0.95.7 successfully.
Both
installed using "pkg install <***>"

Out of interested I wanted to try the more recent WindowMaker 0.95.8
and 
downloaded the source from http://windowmaker.org/.  I followed the
how-to
of extract and configure steps but am having problems with .configure
step.
The script stops with the information:-

  "checking for Xmu library... configure: error: library Xmu not found"

however, Xmu library seems to be installed as reported by cd'ing to 
/usr/local/ports/x11-toolkits/libXmu/ and issuing "make install clean".
The command reports the library is already installed.  Also I find the
*.h
at /usr/local/include/X11/Xmu.  However I cannot find a .lib file -
should
I be able to, and if so why does ports think it is installed.

Clearly, I am misunderstanding what the error message is telling me.
Thus, 
I would be grateful if someone could give me hint of what is going on,
I have Googled extensively but cannot work through this issue - so am 
posting here.

Many thanks for any help!