buildroot: Integrate 2017.08.1 stable release

There are no updated package versions that directly affect our firmware,
but there are fixes to the build process that are worth integrating.

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/buildroot b/buildroot
index 5e23247..6ddc3b3 160000
--- a/buildroot
+++ b/buildroot
@@ -1 +1 @@
-Subproject commit 5e232471b49a2e6c9a79de04e655f3c298fcfa1d
+Subproject commit 6ddc3b3e64d91ac3f3e4400ce3e66100092db548