Force LC_ALL=C.UTF-8 during build

So that builds in non-English locales can pass their build-time tests.

debian/changelog

@@ -1,3 +1,10 @@
+ostree (2016.11-2) UNRELEASED; urgency=medium
+
+  * Force LC_ALL=C.UTF-8 during build, so that builds in non-English
+    locales can pass their build-time tests
+
+ -- Simon McVittie <smcv@debian.org>  Sat, 08 Oct 2016 15:37:36 +0100
+
 ostree (2016.11-1) unstable; urgency=medium
 
   * New upstream release

debian/rules

@@ -2,6 +2,8 @@
 
 export DEB_BUILD_MAINT_OPTIONS = hardening=+all
 export DEB_LDFLAGS_MAINT_APPEND = -Wl,--as-needed
+# Some tests assert that we will see English strings
+export LC_ALL=C.UTF-8
 
 %:
 	dh $@ --with=gir