create bin dir

Makefile

@@ -24,6 +24,7 @@ all: $(EXEC)
 
 # Rule to link the object files into the final executable
 $(EXEC): $(OBJECTS)
+	@mkdir -p $(BIN_DIR)   # Make sure the bin dir exists
 	$(CXX) $(OBJECTS) -o $(EXEC) $(LDFLAGS)
 
 # Rule to compile .cpp files into .o files