Use mpicc to compile, better than CC for MPI applications

Makefile

 CFLAGS = -g -O0 -Wall
 
-
 all: swiftmpistepsim
 
 swiftmpistepsim: swiftmpistepsim.c mpiuse.c mpiuse.h atomic.h cycle.h clocks.h clocks.c
-	$(CC) $(CFLAGS) -o swiftmpistepsim swiftmpistepsim.c mpiuse.c clocks.c -I/usr/include/mpi -lmpi -lpthread
+	mpicc $(CFLAGS) -o swiftmpistepsim swiftmpistepsim.c mpiuse.c clocks.c
 
 clean:
-	rm swiftmpistepsim
+	rm -f swiftmpistepsim