/usr/include/ is in lv2-c++-tools 1.0.5-4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/lv2-c++-tools/
/usr/include/lv2-c++-tools/lv2.h
/usr/include/lv2-c++-tools/lv2_contexts.h
/usr/include/lv2-c++-tools/lv2_event.h
/usr/include/lv2-c++-tools/lv2_event_helpers.h
/usr/include/lv2-c++-tools/lv2_osc.h
/usr/include/lv2-c++-tools/lv2_saverestore.h
/usr/include/lv2-c++-tools/lv2_ui.h
/usr/include/lv2-c++-tools/lv2_ui_presets.h
/usr/include/lv2-c++-tools/lv2_uri_map.h
/usr/include/lv2-c++-tools/lv2gui.hpp
/usr/include/lv2-c++-tools/lv2plugin.hpp
/usr/include/lv2-c++-tools/lv2synth.hpp
/usr/include/lv2-c++-tools/lv2types.hpp