Fix indexing script for base directory of config file

Change-Id: I56937e60792f9b402087ae7ee643fabc2cc27af9
diff --git a/bin/corpuslist_to_index b/bin/corpuslist_to_index
index 260c9c3..7d02f89 100644
--- a/bin/corpuslist_to_index
+++ b/bin/corpuslist_to_index
@@ -42,7 +42,7 @@
 # Make paths absolute
 $json_dir   = File::Spec->rel2abs( $json_dir, $base_dir) if $json_dir;
 $tar_dir    = File::Spec->rel2abs( $tar_dir, $base_dir) if $tar_dir;
-$index_conf = File::Spec->rel2abs( $base_dir, $index_conf) if $index_conf;
+$index_conf = File::Spec->rel2abs( $index_conf, $base_dir) if $index_conf;
 
 
 use feature 'say';