fix makefile

exercises/MPI_examples/manager-worker/Makefile

@@ -5,15 +5,18 @@ CC = mpicc
 CFLAGS = -Wall -std=c11
 CFLAGS += -I. # add the current directory to the include path
 
+.PHONY: all
+all: $(PROG1) $(PROG2) # build the program
+
 $(PROG1): manager.o
 	$(CC) $(CFLAGS) $^ -o $@
 
 $(PROG2): worker.o
 	$(CC) $(CFLAGS) $^ -o $@
 
-.Phone: run
+.PHONY: run
 run: $(PROG1) $(PROG2) # build and run the program
-	MY_MPIRUN_OPTIONS="-usize 8" mpirun -np 4 ./$(PROG1)
+	mpirun -np 1 ./$(PROG1)
 
 $(OBJECTS): %.o: %.c  # compile the source files into object files
 	$(CC) $(CFLAGS) -c $<