Add link flags ocamlmklib when using ctypes stubs. #25909

Job	Run time
Coq 8.16.1	9m 22s
Build (macos-latest, 4.14.x)	26m 7s
Create local opam switch (macos-latest, 5)	9m 12s
Build (ubuntu-latest, 4.14.x)	11m 54s
Coverage (4.14.x)	11m 51s
Create local opam switch (macos-latest, 4.14)	11m 47s
Build (windows-latest, 4.14.x)	7m 4s
MSVC 4.14.0 / windows_x86	11m 40s
Create local opam switch (ubuntu-latest, 5)	5m 37s
Build (ocaml-variants.5.2.0+trunk, ubuntu-latest, true)	2m 42s
MSVC 4.14.0 / windows_x86_64	11m 40s
Documentation	36s
Create local opam switch (ubuntu-latest, 4.14)	5m 18s
Build (5.1.x, ubuntu-latest, true)	2m 42s
Build (5.1.x, macos-latest, true)	4m 53s
Format	2m 28s
Build (4.13.x, ubuntu-latest, true)	3m 17s
Nix (macos-latest)	3m 6s
Build (4.08.x, ubuntu-latest, true)	3m 27s
Build monorepo benchmark docker image	3m 55s
Nix (ubuntu-latest)	56s
Build (4.04.x, ubuntu-latest, true, true)	6m 12s
Build (4.02.x, ubuntu-latest, true)	4m 53s
	2h 40m 39s

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