always use developer version, because it is a lot better

flex/flex.spec

@@ -22,7 +22,7 @@
 ##  SUCH DAMAGE. 
 ##  
 
-%define       V_branch      release
+%define       V_branch      devel
 
 %define       V_release     2.5.4a
 %define       V_release_maj 2.5.4