% scons -Q cc -o bar1.o -c bar1.c cc -o bar2.o -c bar2.c cc -o common1.o -c common1.c cc -o common2.o -c common2.c cc -o bar bar1.o bar2.o common1.o common2.o cc -o foo.o -c foo.c cc -o foo foo.o common1.o common2.o