In _setup_util.py.in, we use python provided by environment instead of
the generated one, as the generated python path can be arbitrarily long
(depending on the location of the build directory), and hence reaches
the shebang line limit, causing the script to fail at start-up.

The catkin developers changed the cmake-generated template _setup_util.py
to use @PYTHON_EXECUTABLE@ instead of /usr/bin/env python in changeset
bf12b40c2 [1]. We revert this change here to address the issue #384 [2].

[1] https://github.com/ros/catkin/commit/bf12b40c2a93b11c3666619a474d35bcfea20837
[2] https://github.com/bmwcarit/meta-ros/issues/384



Signed-off-by: Lukas Bulwahn <lukas.bulwahn@oss.bmw-carit.de>