Files emitted at do_rootfs time by the user mode emulation qemu (e.g. generation of hwdb.bin, fontconfig cache, etc) end up owned by the build machine user rather than root/root.
Investigation started.
Put on hold, as there is no easy technical solution.
Moved to 2.1, 2.0 is already frozen feature-wise.
This is due to the fact that the qemuwrapper running in user space can not get access to pseudo.so to intercept the system call correctly (08:11:36 AM) sgw_: ERROR: ld.so: object 'libpseudo.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored. Trying to add libpseudo.so to the target would cause contamination in the target. The workaround for this is to correct set the ownership / permissions in postinst scripts that calls the qemurapper with the the PSEUDO_UNLOAD such that they chown/chmod is called with pseudo correctly.
When a qemu process is executed the LD_PRELOAD will be run. The LD_PRELOAD if inherited into the target environment will not execute, as it's is designed to be running native and not target. The system may choose to unload pseudo BEFORE calling qemu, if this is the case then any files created or modified by the pseudo method will not be under pseudo control, and thus inherit a system based user or password. I believe this is a problem with the way QEMU is executing individual binaries, and not an error in pseudo itself.
Verified as Wontfix since the problem is not in Yocto project.