link X11 automatically

I was trying to compile (make) a program that uses X11.  Below is the 
compile line followed by the error message:

gcc  hi.o s7_comp.a s7_data.a seed7_05.a -lX11 -lncurses -lm -o hi
/usr/bin/ld: can't locate file for: -lX11

After some searching I found the location of libX11:
/usr/X11R6/lib/libX11.dylib

So I made this change to the makefile:

LFLAGS = -L/usr/X11R6/lib

And now it works:
gcc -L/usr/X11R6/lib hi.o s7_comp.a s7_data.a seed7_05.a -lX11 -lncurses 
-lm -o hi

So my question is, is there a way to have /usr/X11R6/lib added to the 
standard ld lib search chain?  This program is built on Linux, which I 
assume has X11 in the standard search chain.  (Perhaps a bad assumption!)

Thanks,
Frank