systemd/README.build-in-place.md

Building systemd rpms for local development using rpmbuild --build-in-place

This approach is based on filbranden's git-rpmbuild and his talk during ASG2019.

git clone https://github.com/systemd/systemd
fedpkg clone systemd fedora-systemd
cd systemd
rpmbuild -bb --build-in-place --noprep --define "_sourcedir $PWD/../fedora-systemd" --define "_rpmdir $PWD/rpms" --with upstream ../fedora-systemd/systemd.spec
sudo dnf upgrade --setopt install_weak_deps=False rpms/*/*.rpm

--without lto and --without tests may be useful to speed up the build.