-EXTRA_DIST += unistd_.h
-
-# We need the following in order to create <unistd.h> when the system
-# doesn't have one.
-unistd.h: unistd_.h
- cp $(srcdir)/unistd_.h $@-t
- mv $@-t $@
-MOSTLYCLEANFILES += unistd.h unistd.h-t
+
+# We need the following in order to create an empty placeholder for
+# <unistd.h> when the system doesn't have one.
+unistd.h:
+ echo '/* Empty placeholder for $@. */' >$@
+MOSTLYCLEANFILES += unistd.h