Work around failure to build on mips by using cabal, not Setup, to build in debian/rules.

debian/cabal-wrapper

@@ -0,0 +1,16 @@
+#!/bin/sh
+# It would be more usual to use:
+#   export CABAL=./Setup
+# But Setup currently has a very bad dependency resolver, and very bad
+# debugging output, and tends to eat all memory and die on small buildds.
+#
+# This should be revisited once Debian has a newer ghc than 7.6.3,
+# and hopefully gets the improved dependency resolver from cabal.
+set -e
+
+# Avoid cabal writing to HOME, and avoid local cabal settings
+# influencing the build.
+HOME=$(mktemp -d)
+export HOME
+
+cabal "$@"