/usr/include/libcalamares/ is in calamares 3.1.12-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libcalamares/CalamaresConfig.h
/usr/include/libcalamares/CppJob.h
/usr/include/libcalamares/DllMacro.h
/usr/include/libcalamares/GlobalStorage.h
/usr/include/libcalamares/Job.h
/usr/include/libcalamares/JobQueue.h
/usr/include/libcalamares/PluginDllMacro.h
/usr/include/libcalamares/ProcessJob.h
/usr/include/libcalamares/PythonHelper.h
/usr/include/libcalamares/PythonJob.h
/usr/include/libcalamares/PythonJobApi.h
/usr/include/libcalamares/Typedefs.h
/usr/include/libcalamares/kdsingleapplicationguard/
/usr/include/libcalamares/kdsingleapplicationguard/kdlockedsharedmemorypointer.h
/usr/include/libcalamares/kdsingleapplicationguard/kdsharedmemorylocker.h
/usr/include/libcalamares/kdsingleapplicationguard/kdsingleapplicationguard.h
/usr/include/libcalamares/kdsingleapplicationguard/kdtoolsglobal.h
/usr/include/libcalamares/kdsingleapplicationguard/pimpl_ptr.h
/usr/include/libcalamares/utils/
/usr/include/libcalamares/utils/CalamaresUtils.h
/usr/include/libcalamares/utils/CalamaresUtilsSystem.h
/usr/include/libcalamares/utils/Logger.h
/usr/include/libcalamares/utils/PluginFactory.h
/usr/include/libcalamares/utils/PluginFactory_p.h
/usr/include/libcalamares/utils/Retranslator.h
/usr/include/libcalamares/utils/Units.h