update.sh: Fixed execution of missing configure script

update.sh

@@ -7,12 +7,15 @@ if [ $# -eq 1 ]; then
 fi
 
 PREFIX=release;
+CONF_SCRIPT="configure.sh";
 
 git pull --tags > /dev/null;
 TAG=$(git tag --list | grep "^$PREFIX-" | sort -r | head -n 1);
 if git verify-tag --raw "$TAG" 2>&1 | grep "TRUST_ULTIMATE" > /dev/null; then
     git checkout "$TAG";
-    ./configure.sh;
+    if [ -f "$CONF_SCRIPT" ]; then
+        ./$CONF_SCRIPT;
+    fi
 else
     echo "Invalid or missing signature for $TAG" >&2;
     exit 1;