useorocos: fixed installation of empty directory for packages if DESTDIR environment variable is set (required for building Debian packages)

Signed-off-by: Johannes Meyer <johannes@intermodalics.eu>
useorocos: re-enable auto-linking also for catkin builds

Signed-off-by: Johannes Meyer <johannes@intermodalics.eu>
Merge branch 'enable_autolinking_for_catkin' of https://github.com/meyerj/rtt into toolchain-2.7