Fix check for setup.cfg in build_ament_python.sh.in

[traversaro]

Fix #46 by reverting 8be7ab8 . To actually fix the regression of RoboStack/ros-humble#41 we need a rebuild of affected packages.

[Tobias-Fischer]

Does that affect both linux and osx?

[traversaro]

Does that affect both linux and osx?

I guess yes, but I did not directly checked.

[Tobias-Fischer]

Unfortunately the state is worse than before now. Copying from Slack:
ament-copyright does not have a setup.cfg. The pip variant installs the binaries in the correct path (bin), whereas the setup.py variant does not. So pip should be used, but currently setup.py is used.

demo-nodes-py does have a setup.cfg. So pip is used. However, it does not respect the install_scripts instructions within. Coincidentally, the setup.py variant would install the binaries in the correct location

It is almost as if the if condition should be negated.

[traversaro]

Thanks, I was looking into that as well.

[traversaro]

It is almost as if the if condition should be negated.

I did exactly this in #49, and it seems to work (tested in ament-copyright and in demo-nodes-py).