Makefile: remove test-chmtime program in target clean.

While running 'make test', the test-chmtime program is created, and should
be cleaned up on 'make clean'.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -963,7 +963,7 @@ dist-doc:
 
 clean:
 	rm -f *.o mozilla-sha1/*.o arm/*.o ppc/*.o compat/*.o xdiff/*.o \
-		$(LIB_FILE) $(XDIFF_LIB)
+		test-chmtime$X $(LIB_FILE) $(XDIFF_LIB)
 	rm -f $(ALL_PROGRAMS) $(BUILT_INS) git$X
 	rm -f *.spec *.pyc *.pyo */*.pyc */*.pyo common-cmds.h TAGS tags
 	rm -rf autom4te.cache