The following is the command to use when compiling on Sandcastle to have
freeimage, glut and X-window working.

gcc -O2 -s -o $1 $1.c -L /usr/X11R6/lib64
-lc /usr/local/lib64/libfreeimage.a /usr/local/lib64/libglut.a -lGL
-lGLU -lX11 -lXmu -lXi -lXext -lm

where $1 is the filename without the .c extension.

Furthermore, when including the header files in the program make use of
the following:

#include <GL/gl.h>
#include "/usr/local/include/FreeImage.h"
#include "/usr/local/include/GL/glut.h"

-- Pascal Comte.