[wip/roscontrol-sot] Fix workspace inclusion chaining pb.

pkg-config.cmake in jrl-cmakemodules is using INCLUDE_DIRECTORIES with SYSTEM option.
The order of directories for the header files is therefore change as this option
uses -isystem instead of -I.
The package is then compiled against the system ros-control package
instead of using prf-ros-control.
The patch of this commit fix this problem.