Fix thread-issue starting with ctypes.0.18.0 - ocaml/opam-repository#…

…17614

Makefile

@@ -35,23 +35,23 @@ hanoi:
 	ocamlbuild -use-ocamlfind -package qcheck,qcstm,ppx_deriving.show examples/hanoi.cma examples/hanoi.native
 
 putget: putgetstub.so
-	ocamlbuild -use-ocamlfind -package ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show examples/putget.native
+	ocamlbuild -use-ocamlfind -tag thread -package ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show examples/putget.native
 
 putgetstub.so: examples/putgetstub.c
 	if [[ ! -d _build ]]; then mkdir _build; fi
 	if [[ ! -d _build/examples ]]; then mkdir _build/examples; fi
 	gcc -shared -o _build/examples/putgetstub.so -fPIC examples/putgetstub.c
 
 stdio: stdiostub.o
-	ocamlbuild -use-ocamlfind -package ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show -lflags -custom,examples/stdiostub.o examples/stdio.cma examples/stdio.top
-	ocamlbuild -use-ocamlfind -package ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show -lflags examples/stdiostub.o examples/stdio.native
+	ocamlbuild -use-ocamlfind -tag thread -package threads,ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show -lflags -custom,examples/stdiostub.o examples/stdio.cma examples/stdio.top
+	ocamlbuild -use-ocamlfind -tag thread -package threads,ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show -lflags examples/stdiostub.o examples/stdio.native
 
 stdiostub.o: examples/stdiostub.c
 	ocamlbuild examples/stdiostub.o
 
 cq: cqstub.o
-	ocamlbuild -use-ocamlfind -package ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show -lflags -custom,examples/cqstub.o examples/cq.cma examples/cq.top
-	ocamlbuild -use-ocamlfind -package ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show -lflags examples/cqstub.o examples/cq.native
+	ocamlbuild -use-ocamlfind -tag thread -package threads,ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show -lflags -custom,examples/cqstub.o examples/cq.cma examples/cq.top
+	ocamlbuild -use-ocamlfind -tag thread -package threads,ctypes,ctypes.foreign,qcheck,qcstm,ppx_deriving.show -lflags examples/cqstub.o examples/cq.native
 
 cqstub.o: examples/cqstub.c
 	ocamlbuild examples/cqstub.o