[Caml-list] ocamlbuild add unexpected directories to including-dirs while building multi-targets

[ZAN DoYe <zandoye@gmail.com>]

suppose the dir tree is:

.
├── a
│   ├── a.ml (let v= I.a)
│   ├── i
│   │   └── i.ml (let a= 1)
│   └── _tags ("i": include)
├── b
│   ├── b.ml (let v= I.b)
│   ├── i
│   │   └── i.ml (let b= 1)
│   └── _tags ("i": include)
├── myocamlbuild.ml (an empty file)
└── o.itarget (a/a.byte \n b/b.byte)

after running ocamlbuild o.otarget, the error info:

Finished, 1 target (0 cached) in 00:00:00.
+ /home/kandu/.opam/4.02.3/bin/ocamlc.opt -c -I a -I b/i -I a/i -o a/a.cmo a/a.ml
File "a/a.ml", line 1, characters 7-10:
Error: Unbound value I.a

Is there any way to isolate including-dirs while compiling multi-targets?