Error in cmake on Linux - xenomai : Optional library RTT_PLUGIN_rtt-marshalling NOT FOUND

Dear Sirs,

I am in trouble in generating a deployments on Linux with xenomai.
I generate my application using orogen with the command

orogen --target=xenomai -v rosetta.orogen

then I create a build directory with the commands:

mkdir build
cd build

Running the command

cmake ..

from the inside of the buil directory
I get the following outputs

cmake ..
-- Could NOT find Doxygen (missing: DOXYGEN_EXECUTABLE)
-- documentation generation disabled
-- Orocos reports in /root/orocos/install/include/rtt/transports/corba/rtt-corba-config.h to use the OMNIORB
-- OCL found, the generated task library will be compatible with the deployer component
-- Optional library RTT_PLUGIN_rtt-marshalling NOT FOUND. If the library is already installed, use the RTT_PLUGIN_rtt-marshalling_ROOT_DIR environment variable or ccmake to set the missing variables manually.
-- Found RTT_PLUGIN_rtt-typekit
-- Found RTT_PLUGIN_rtt-transport-corba
-- Optional library RTT_PLUGIN_rtt-marshalling NOT FOUND. If the library is already installed, use the RTT_PLUGIN_rtt-marshalling_ROOT_DIR environment variable or ccmake to set the missing variables manually.
-- Configuring done
-- Generating done
-- Build files have been written to: /root/rock/Rosetta10/build

I verified that in in my orocos installation directory

/root/orocos/install/lib/orocos/xenomai/plugins/

in this directory I have the library

librtt-marshalling-xenomai.so

which I need to use.

So I tried again with the command

cmake .. -DRTT_PLUGIN_rtt-marshalling_ROOT_DIR=/root/orocos/install/lib/orocos/xenomai/plugins/librtt-marshalling-xenomai.so

but I get the same error listed here below

cmake .. -DRTT_PLUGIN_rtt-marshalling_ROOT_DIR=/root/orocos/install/lib/orocos/xenomai/plugins/librtt-marshalling-xenomai.so
-- Could NOT find Doxygen (missing: DOXYGEN_EXECUTABLE)
-- documentation generation disabled
-- Orocos reports in /root/orocos/install/include/rtt/transports/corba/rtt-corba-config.h to use the OMNIORB
-- OCL found, the generated task library will be compatible with the deployer component
-- Optional library RTT_PLUGIN_rtt-marshalling NOT FOUND. If the library is already installed, use the RTT_PLUGIN_rtt-marshalling_ROOT_DIR environment variable or ccmake to set the missing variables manually.
-- Found RTT_PLUGIN_rtt-typekit
-- Found RTT_PLUGIN_rtt-transport-corba
-- Optional library RTT_PLUGIN_rtt-marshalling NOT FOUND. If the library is already installed, use the RTT_PLUGIN_rtt-marshalling_ROOT_DIR environment variable or ccmake to set the missing variables manually.
-- Configuring done
-- Generating done
-- Build files have been written to: /root/rock/Rosetta10/build

What have I missed?

Thank you in advance for your kind support.

Gianpaolo Rizzi