Add missing flambda2_datalog.cma to merge_archives (#3582)

* Add test for linking to ocamloptcomp

* Add missing flambda2_datalog.cma to merge_archives

Author: bclement-ocp

dune

@@ -693,6 +693,7 @@
    %{dep:middle_end/flambda2/import/flambda2_import.a}
    %{dep:middle_end/flambda2/ui/flambda2_ui.a}
    %{dep:middle_end/flambda2/algorithms/flambda2_algorithms.a}
+   %{dep:middle_end/flambda2/datalog/flambda2_datalog.a}
    %{dep:middle_end/flambda2/numbers/floats/flambda2_floats.a}
    %{dep:middle_end/flambda2/numbers/flambda2_numbers.a}
    %{dep:middle_end/flambda2/kinds/flambda2_kinds.a}
@@ -731,6 +732,7 @@
    %{dep:middle_end/flambda2/import/flambda2_import.cma}
    %{dep:middle_end/flambda2/ui/flambda2_ui.cma}
    %{dep:middle_end/flambda2/algorithms/flambda2_algorithms.cma}
+   %{dep:middle_end/flambda2/datalog/flambda2_datalog.cma}
    %{dep:middle_end/flambda2/numbers/floats/flambda2_floats.cma}
    %{dep:middle_end/flambda2/numbers/flambda2_numbers.cma}
    %{dep:middle_end/flambda2/kinds/flambda2_kinds.cma}
@@ -769,6 +771,7 @@
    %{dep:middle_end/flambda2/import/flambda2_import.cmxa}
    %{dep:middle_end/flambda2/ui/flambda2_ui.cmxa}
    %{dep:middle_end/flambda2/algorithms/flambda2_algorithms.cmxa}
+   %{dep:middle_end/flambda2/datalog/flambda2_datalog.cmxa}
    %{dep:middle_end/flambda2/numbers/floats/flambda2_floats.cmxa}
    %{dep:middle_end/flambda2/numbers/flambda2_numbers.cmxa}
    %{dep:middle_end/flambda2/kinds/flambda2_kinds.cmxa}

testsuite/tests/link-test/link_ocamloptcomp.ml

@@ -0,0 +1,27 @@
+(* TEST
+ {
+   setup-ocamlc.byte-build-env;
+   module = "link_ocamloptcomp.ml";
+   ocamlc.byte with ocamlcommon;
+   module = "";
+   flags = "-linkall";
+   all_modules = "";
+   program = "link_ocamloptcomp.cma";
+   libraries += "ocamloptcomp";
+   ocamlc.byte;
+   check-ocamlc.byte-output;
+ }{
+   setup-ocamlopt.byte-build-env;
+   module = "link_ocamloptcomp.ml";
+   ocamlopt.byte with ocamlcommon;
+   module = "";
+   flags = "-linkall";
+   all_modules = "";
+   program = "link_ocamloptcomp.cmxa";
+   libraries += "ocamloptcomp";
+   ocamlopt.byte;
+   check-ocamlopt.byte-output;
+ }
+*)
+(* If this test fails, a new library likely needs to be added to the
+   ocamloptcomp_with_flambda2 rules in the top-level dune file. *)