When called with --disable-dependency-tracking, the configure
script would exit with the usage output. This patch make the script
accept and ignore that option.

Index: configure
===================================================================
--- configure.orig	2009-04-27 15:19:03.000000000 +0100
+++ configure	2011-12-22 16:46:32.000000000 +0000
@@ -20,7 +20,7 @@ strip=1
 arch=`uname -s`
 
 while [ -n "$1" ]; do
-	e="`expr "$1" : '--\(.*=.*\)'`"
+	e="`expr "$1" : '--\(.*\)'`"
 	if [ -z "$e" ]; then
 		cat<<EOF
 Axel configure
@@ -44,8 +44,10 @@ EOF
 	
 	keyname=$(expr "$e" : '\(.*\)=.*' | sed 's/[^a-z0-9_]/_/g')
 	value=$(expr "$e" : '.*=\(.*\)' | sed "s/'/_/g")
-	
-	eval "$keyname='$value'"
+
+	if [ -n "$value" ]; then
+		eval "$keyname='$value'"
+	fi
 	shift;
 done