Added EPO4 as env variable in external script

Author: jackal1-66

MC/config/examples/epos4/epos.sh

@@ -31,5 +31,10 @@ if [ -z "${LIBDIR}" ]; then
     export LIBDIR=$EPOS4_ROOT/epos4/bin
 fi
 
+# Check if the environment variable EPO4 is set (important with o2dpg-sim-tests on CI machines)
+if [ -z "${EPO4}" ]; then
+    export EPO4=$EPOS4_ROOT/epos4/
+fi
+
 # Or filters the stdout with only HepMC2 useful data
 $EPOS4_ROOT/epos4/scripts/epos -hepstd -s $seed $optns | sed -n 's/^\(HepMC::\|[EAUWVP] \)/\1/p'