The Linux Kernel, Debian packages, and fakeroot.
In a vain attempt to let more people stumble across this, the “deb-pkg” target in the Linux Kernel makefile now needs to be run with fakeroot -u instead of fakeroot, due to a change in the way scripts/setlocalversion tracks down the current git version.
I plan on taking another look at the builddeb script to see about incorporating this into it, internally, but I also need to verify if the build process for a rpm needs to be run as root or if it can run as any user.