FIXME: upstream should provide a hurddir ./configure parameter instead

Index: hurd-debian/config.make.in
===================================================================
--- hurd-debian.orig/config.make.in
+++ hurd-debian/config.make.in
@@ -20,7 +20,7 @@ prefix = @prefix@
 exec_prefix = @exec_prefix@
 
 # Directories where things get installed.
-hurddir = ${exec_prefix}/hurd
+hurddir = /hurd
 libdir = @libdir@
 bindir = @bindir@
 sbindir = @sbindir@
