How to compile:
First, install Geant4.
Make sure all your G4* environment variables are set.
Then simply
./configure
[answer the question]
make
The executable binary will be in $G4WORK/$G4SYSTEM/glg4sim.
If you are _re_compiling after moving directories around, then
do a "make clean" before the "make", to delete any dependency
files left around from compilation in the other directories.
Sometimes "make clean" is necessary under other circumstances, too.
A general rule for big C++ projects is: if "make" fails after a change,
try "make clean && make".