ocamlbuild: path problem with libraries

[Hugo Ferreira <hmf@inescporto.pt>]

Hello,

I have a project with the directories: src, lib and cudd
In cudd I have third party libraries and cm and mli files. When I
execute a command line with a full path to the cudd libraries
so:

PROJ_PATH="cudd,src"
ocamlbuild -no-hygiene -Is $PROJ_PATH -lib cudd -cflags 
-I,/home/hugof/workspace/planner/cudd -lflags 
-I,/home/hugof/workspace/planner/cudd -verbose 100 src/parser.native

everything works as expected. However, using relative paths:

PROJ_PATH="cudd,src"
ocamlbuild -no-hygiene -Is $PROJ_PATH -lib cudd -cflags -I,cudd -lflags 
-I,cudd -verbose 100 src/parser.native

I get:

+ /home/hugof/ocaml/godi/bin/ocamlopt.opt -I cudd cudd.cmxa -g -p 
src/parser.cmx -o src/parser.native
Cannot find file cudd.cmxa

How can I set-up ocamlbuild so that relative paths can be used?
Note that I get the same consistent behaviour when using the
myocamlbuild.ml file.

TIA,
Hugo F.