Duplicate libraries in fox-config output

Hi,
I have a question about the output of "fox-config --libs".
On my system it currently gives: "-L/usr/lib64 -lFOX-1.6 -lX11 -lXext 
-lfreetype -lfontconfig -lXft -lXcursor -lXrender -lXrandr -lXfixes -lXi 
-lGL -lGLU -ldl -lpthread -lrt -ljpeg -lpng -ltiff -lz -lbz2 -lGLU -lGL"
which duplicates the GL and GLU libraries.

The problem is that recent macOS builds complain if you link the same 
library twice.

I had a look at the source code in configure.ac and fox-config.in and 
this seems to be intentional because indeed the GL libraries (LIBGL) are 
being added to the LIBS variable and then both are output in the end.
I removed the first addition of the GL libs and it is still working fine 
here but before submitting a patch I wanted to ask whether there is a 
known reason for this duplication because sometimes the linker is tricky.

Thank you and best regards,
Michael