Proton Vendor package that is used to package Proton as a ROS 2 package.
By default, this package downloads and builds Proton from GitHub. For development with local Proton changes, you can use Proton from the same workspace:
colcon build --cmake-args -DPROTON_VENDOR_USE_LOCAL=ON --symlink-install
Ensure Proton is cloned in the same workspace when using this option.