main/dtc: add py3-libfdt subpackage
pylibfdt is included in the dtc sources and allows using libfdt from Python.
For some reason, the pylibfdt Makefile ignores
$(DESTDIR) at the
moment. Add a small patch to fix this so the Python library is
This is just temporary, the next release will introduce Meson build scripts which do not seem to have that problem.