*: add pause binary as a build target

Take the pause binary's source code (from kubernetes/pause) and make it
part of the build setup for cri-o. This is necessary to remove the
Docker requirement for setting up the pause container, at least until
the storage API is set up so that we can make this far more flexible
(namely that we can pull the image from a registry or other transport,
even from an archive).

Signed-off-by: Aleksa Sarai <asarai@suse.de>

pause/Makefile

@@ -0,0 +1,13 @@
+src = $(wildcard *.c)
+obj = $(src:.c=.o)
+
+override LIBS +=
+override CFLAGS += -Os -Wall -Wextra -static
+
+pause: $(obj)
+	$(CC) -o $@ $^ $(CFLAGS) $(LIBS)
+	strip $@
+
+.PHONY: clean
+clean:
+	rm -f $(obj) pause