QEMU guest agent hardcodes paths to /sbin/hwclock and /sbin/shutdown. Patch
the source to try binaries under /run/current-system/profile/sbin first.
* gnu/packages/patches/qemu-fix-agent-paths.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register the patch.
* gnu/packages/virtualization.scm (qemu)[origin]: Apply it.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
