flambda-backend: Install dynlink.cmt (#1999)

Author: mshinwell

otherlibs/dynlink/dune

@@ -445,6 +445,7 @@
 (install
   (files
     (.dynlink_internal.objs/byte/dynlink.cmti as dynlink/dynlink.cmti)
+    (.dynlink_internal.objs/byte/dynlink.cmt as dynlink/dynlink.cmt)
     (.dynlink_internal_common.objs/native/dynlink_common.cmx
     as
     dynlink/dynlink_common.cmx)