add headers_lib

src/dune

@@ -1,8 +1,25 @@
 (executable
  (public_name mte)
  (name mte)
- (modules assets assets_crunch headers mte config util syntax)
- (libraries vif fmt jsont cohttp))
+ (modules assets assets_crunch headers mte config util)
+ (libraries
+  headers_lib
+  syntax
+  ;
+  vif
+  fmt
+  jsont
+  cohttp))
+
+(library
+ (name headers_lib)
+ (modules headers_lib)
+ (libraries fmt syntax))
+
+(library
+ (name syntax)
+ (modules syntax)
+ (libraries))
 
 (rule
  (target assets_crunch.ml)