Xenomai 2/3 support update

[ahoarau]

This goes with orocos-toolchain/rtt#301 on rtt.
Builds fine on xenomai 2.x and 3.x.
I think I already asked, but isnt there a way to export the Findxxx.cmake from rtt ?

[meyerj]

Thanks for your valuable contribution!

I think I already asked, but isnt there a way to export the Findxxx.cmake from rtt ?

Yes. I do not see a problem with installing FindXenomai.cmake to lib/cmake/orocos-rtt (${CONFIG_FILE_PATH}) alongside other cmake configuration files in rtt/CMakeLists.txt. Then any depending package can include the file after OROCOS-RTT has been found using

find_package(OROCOS-RTT REQUIRED)
# or find_package(rtt_ros) or find_package(catkin REQUIRED COMPONENTS rtt_ros) in a ROS context

# Link against Xenomai POSIX skin to get
if(OROCOS_TARGET STREQUAL "xenomai")
  list(APPEND CMAKE_MODULE_PATH "${OROCOS-RTT_DIR}")
  find_package(Xenomai REQUIRED)

  # ...
endif()

I would not add ${OROCOS-RTT_DIR} to the CMAKE_MODULE_PATH by default in the RTT cmake config or even include it implicitly from orocos-rtt-config.cmake to reduce the risk of conflicts with modules of the same name in other packages.

For me it would be acceptable to already remove the Xenomai cmake scripts from this repo and install the new file in orocos-toolchain/rtt#301. The old scripts would probably not have worked anymore anyway, at least not for Xenomai 3.

Side note: The same applies for other custom CMake config files, e.g. for CORBA. Some package redistribute them, e.g. kdl_typekit.

[ahoarau]

Excellent, let's go with installing all those cmake files.

1. In order to make things coherent, the variables generated by Find<PkgName>.cmake should be <PkgName>_LIBRARIES etc. Here we have XENOMAI_LIBRARIES for backwards compatibility, but I'm fine with updating it.

2. Shall we change the name of the file ? I'm concerned people will load the ROS cmake_modules and executing the FindXenomai.cmake included.

[ahoarau]

rebased from 2.10 + fix compilation on clang (c++ mangling)