Set LC_ALL=C.UTF-8 for all builds

Upstream sets LC_ALL=C when building most things, and we do that in
one place to ensure consistent ordering.  However the encoding of HTML
docs still differs.  Choose 'C.UTF-8' instead of 'C' because it makes
the HTML docs slightly smaller.

debian/changelog

@@ -10,6 +10,8 @@ linux (4.2~rc7-1~exp1) UNRELEASED; urgency=medium
 
   [ Ben Hutchings ]
   * debian/control: Correct build-dependency on xz-utils, needed on all arches
+  * Fix more issues that prevent a reproducible build:
+    - Set LC_ALL=C.UTF-8
 
  -- Ben Hutchings <ben@decadent.org.uk>  Mon, 17 Aug 2015 10:28:46 +0200
 

debian/rules.real

@@ -33,6 +33,7 @@ endif
 export PYTHONPATH = $(CURDIR)/debian/lib/python
 export DH_OPTIONS
 export DEB_HOST_ARCH DEB_HOST_GNU_TYPE DEB_BUILD_ARCH
+export LC_ALL = C.UTF-8
 
 include debian/rules.defs
 
@@ -90,7 +91,7 @@ $(BUILD_DIR)/linux-source-$(UPSTREAMVERSION).tar.xz: $(STAMPS_DIR)/source
 	find '$(DIR)' -depth -newermt '$(SOURCE_DATE)' -print0 | \
 		xargs -0r touch --no-dereference --date='$(SOURCE_DATE)'
 	cd '$(BUILD_DIR)'; find 'linux-source-$(UPSTREAMVERSION)' -print0 | \
-		LC_ALL=C sort -z | \
+		sort -z | \
 		xargs -0 tar --no-recursion -raf 'linux-source-$(UPSTREAMVERSION).tar.xz'
 	rm -rf '$(DIR)'