-currently in NetBSD 8.99...

===> Summary of results:
         build.sh command:    ./build.sh -j 4 -u -x -X /usr/xsrc release sets sourcesets iso-image-source
         build.sh started:    Sun Jul 28 10:03:40 UTC 2019
         NetBSD version:      8.99.51
         MACHINE:             amd64
         MACHINE_ARCH:        x86_64
         Build platform:      NetBSD 8.99.51 amd64
         HOST_SH:             /bin/sh
         MAKECONF file:       /etc/mk.conf
         TOOLDIR path:        /usr/src/obj/tooldir.NetBSD-8.99.51-amd64
         DESTDIR path:        /usr/src/obj/destdir.amd64
         RELEASEDIR path:     /usr/src/obj/releasedir
         Updated makewrapper: /usr/src/obj/tooldir.NetBSD-8.99.51-amd64/bin/nbmake-amd64
         Successful make release
         Building sets from pre-populated /usr/src/obj/destdir.amd64
         Built sets to /usr/src/obj/releasedir/amd64/binary/sets
         Successful make sourcesets
         Successful make iso-image-source
         build.sh ended:      Sun Jul 28 13:39:36 UTC 2019
===> .

...time's wonky because I didn't set the timezone properly; but it took 3.5 hours to (re)build NetBSD-current from NetBSD current in VirtualBox 6.