Compilation problem finding wet packages in rosbuild environment

Hi,

I'm installing iTaSC on an Odroid XU3 small computer using Ubuntu 14.04 and ROS Indigo for ARM.

I've build the required packages in catkin workspace while iTaSC is in a rosbuild environment.
For the installation of the catkin packages I've followed the instructions here to setup the workspace for Orocos and other packages and compile everything:
https://github.com/orocos/rtt_ros_integration/blob/indigo-devel/README.md

So my directories look like this:

ws/ --CATKIN WORKSPACE
underlay_isolated
build_isolated
install_isolated
devel_isolated
src
orocos
orocos_kinematics_dynamics
orocos_toolchain
underlay
build
devel
src
CMakelists.txt
geometry
rtt_geometry
rtt_ros_integration

ros_ws --ROSBUILD WORKSPACE
setup.sh
setup.bash
setup.zsh
.rosinstall
itasc_core
...

My .bashrc:

source /opt/ros/indigo/setup.bash
source ~/ws/underlay/devel/setup.sh
source ~/ros_ws/setup.sh
export PKG_CONFIG_PATH=~/ws/underlay_isolated/install_isolated/lib/pkgconfig:$PKG_CONFIG_PATH
export PKG_CONFIG_PATH=~/ws/underlay/devel/lib/pkgconfig:$PKG_CONFIG_PATH

I'm confident that this setup is correct as everything compiles well and I can find all packages through rospack find manually.
The problem is when I try to rosmake itasc_core (the first package) it cannot find the packages on its own:

odroid@odroid ~/ros_ws $ rosmake itasc_core
[ rosmake ] rosmake starting...
[ rosmake ] Packages requested are: ['itasc_core']
[ rosmake ] Logging to directory /home/odroid/.ros/rosmake/rosmake_output-20130101-012452
[ rosmake ] Expanded args ['itasc_core'] to:
['itasc_core']
[rosmake-0] Starting >>> catkin [ make ]
[rosmake-0] Finished <<< catkin ROS_NOBUILD in package catkin
No Makefile in package catkin
[rosmake-0] Starting >>> rtt [ make ]
[rosmake-2] Starting >>> log4cpp [ make ]
[rosmake-4] Starting >>> orocos_kdl [ make ]
[rosmake-2] Finished <<< log4cpp ROS_NOBUILD in package log4cpp
No Makefile in package log4cpp
[rosmake-0] Finished <<< rtt ROS_NOBUILD in package rtt
No Makefile in package rtt
[rosmake-4] Finished <<< orocos_kdl ROS_NOBUILD in package orocos_kdl
No Makefile in package orocos_kdl
[rosmake-4] Starting >>> ocl [ make ]
[rosmake-4] Finished <<< ocl ROS_NOBUILD in package ocl
No Makefile in package ocl
[rosmake-4] Starting >>> itasc_core [ make ]
[ rosmake ] All 28 linestasc_core: 2.7 sec ] [ 1 Active 5/6 Complete ]
{-------------------------------------------------------------------------------
make: Warning: File `/opt/ros/indigo/share/mk/buildtest.mk' has modification time 7.3e+07 s in the future
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 rtt was not found in the pkg-config search path.
Perhaps you should add the directory containing `rtt.pc'
to the PKG_CONFIG_PATH environment variable
No package 'rtt' found
[rospack] Error: python function 'rosdep2.rospack.call_pkg_config' could not call 'pkg-config --cflags-only-I rtt' 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)