See the attached patch, it's trivial.
>From 715e9e3435c2b4a65e867ed055426c214a9ac9fd Mon Sep 17 00:00:00 2001
From: Alexander Volkov <supp...@rusbitech.ru>
Date: Wed, 7 Dec 2016 18:49:13 +0300
Subject: [PATCH] don't build depend on libkf5config-bin on stage1
---
debian/changelog | 7 +++++++
debian/control | 2 +-
debian/control.in | 2 +-
3 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/debian/changelog b/debian/changelog
index 43be132..0f4598f 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,10 @@
+libproxy (0.4.13-1.2) unstable; urgency=medium
+
+ * Non-maintainer upload.
+ * Don't build depend on libkf5config-bin on stage1
+
+ -- Alexander Volkov <supp...@rusbitech.ru> Wed, 07 Dec 2016 18:46:23 +0300
+
libproxy (0.4.13-1.1) unstable; urgency=medium
* Non-maintainer upload.
diff --git a/debian/control b/debian/control
index b633c8c..d9b560a 100644
--- a/debian/control
+++ b/debian/control
@@ -19,7 +19,7 @@ Build-Depends: debhelper (>= 9.20140227),
python3-all,
network-manager-dev [linux-any],
libdbus-1-dev,
- libkf5config-bin,
+ libkf5config-bin <!stage1>,
libmozjs185-dev (>= 1.8.5) <!stage1>,
libwebkit2gtk-4.0-dev <!stage1>,
libjavascriptcoregtk-4.0-dev <!stage1>,
diff --git a/debian/control.in b/debian/control.in
index 098f3c7..c1a94c7 100644
--- a/debian/control.in
+++ b/debian/control.in
@@ -15,7 +15,7 @@ Build-Depends: debhelper (>= 9.20140227),
python3-all,
network-manager-dev [linux-any],
libdbus-1-dev,
- libkf5config-bin,
+ libkf5config-bin <!stage1>,
libmozjs185-dev (>= 1.8.5) <!stage1>,
libwebkit2gtk-4.0-dev <!stage1>,
libjavascriptcoregtk-4.0-dev <!stage1>,
--
2.8.1
