Fixed makefile

examples/Makefile

@@ -3,7 +3,7 @@ SRCDIR = ..
 # Test programs to compile, and a list of sources for each.
 # To add a new test, put its name on the PROGS list
 # and then add a name_SRC line that lists its source files.
-PROGS = cat cmp cp echo halt hex-dump ls mcat mcp mkdir pwd rm shell \
+PROGS = cat cmp cp echo exit halt hex-dump ls mcat mcp mkdir pwd rm shell \
 	bubsort insult lineup matmult recursor my
 
 # Should work from project 2 onward.