To make it work , following instructions could do help.
#build the omr firstly.
make omr
#clean the omr
make omrclean
#build the som++
make
#clean the som++
make clean
#build the omr and som++ together.
make somrall
#Clean the omr and som++
make somrallclean
#Run the SOM
export LD_LIBRARY_PATH=.
./somr -cp Smalltalk Examples/Hello/Hello.som
./somr -cp Smalltalk Examples/Benchmarks/Sum.som