Orocos using deb and rosbuild


I get this error when trying to rosmake a rosbuild pkg,
that depends on ocl, with orocos installed using ros-indigo-rtt-... debian pkgs.
When I install orocos from source, there is no problem.
Are there extra env vars to be set?
Or do I have to change the manifest.xml file?
It contains the line <depend package="ocl" />

The ROS_PKG_PATH does contain /op/ros/indigo/stacks and share (I can roscd ocl).

My PKG_CONFIG_PATH is set to /opt/ros/indigo/lib/arm-linux-gnueabihf/pkgconfig:/opt/ros/indigo/lib/pkgconfig
The latter contains all orocos related .pc files, including ocl-gnulinux.pc and orocos-ocl-gnulinux.pc.
OROCOS_TARGET is set to gnulinux.

[rosmake-2] Starting >>> itasc_core [ make ]
[ rosmake ] All 27 linestasc_core: 2.6 sec ] [ 1 Active 5/6 Complete ]
mkdir -p bin
cd build && cmake -Wdev -DCMAKE_TOOLCHAIN_FILE=/opt/ros/indigo/share/ros/core/rosbuild/rostoolchain.cmake -DCMAKE_INSTALL_PREFIX=`rospack find itasc_core`/install ..
[rosbuild] Building package itasc_core
[rosbuild] Cached build flags older than manifests; calling rospack to get flags
Failed to invoke /opt/ros/indigo/bin/rospack cflags-only-I;--deps-only itasc_core
Package ocl was not found in the pkg-config search path.
Perhaps you should add the directory containing `ocl.pc'
to the PKG_CONFIG_PATH environment variable
No package 'ocl' found
[rospack] Error: python function 'rosdep2.rospack.call_pkg_config' could not call 'pkg-config --cflags-only-I ocl' without errors

CMake Error at /opt/ros/indigo/share/ros/core/rosbuild/public.cmake:129 (message):

Failed to invoke rospack to get compile flags for package 'itasc_core'.
Look above for errors from rospack itself. Aborting. Please fix the
broken dependency!

Call Stack (most recent call first):
/opt/ros/indigo/share/ros/core/rosbuild/public.cmake:231 (rosbuild_invoke_rospack)
CMakeLists.txt:9 (rosbuild_init)