Download patch instead of requiring it to be installed

Part of work to make the code build on a clean Stretch machine.

Change-Id: I1f7b9b51a84a98bc178b05e575ae4b314cf69c1c
diff --git a/debian/patch.bzl b/debian/patch.bzl
new file mode 100644
index 0000000..fbc014e
--- /dev/null
+++ b/debian/patch.bzl
@@ -0,0 +1,3 @@
+files = {
+    "patch_2.7.5-1+deb8u1_amd64.deb": "5272a26273fd799ec1ec74db0e01df5883abbdf8b7e343ad28227295f660c35d",
+}