If you stay with the Yocto image, you probably never need to run the recovery option with flashall. Because there's a different partitioning scheme with ubilinux, the '-b' option is required, which repartitions the emmc and calls flash-ifwi in the script. This flash-ifwi function uses either phoneflashtool or xfstk-dldr-solo, depending on what's installed. So when I'm running the -b option, I don't have phoneflashtool (and couldn't find it on the net), so I'm left with the option of installing xfstk (i.e. building from source)
xFSTK only seems to build on 32-bit ubuntu, as it explicitly requires linking against a 32-bit version of libusb.a. xFSTK refuses to build on a 64-bit OS for me.
So as long as you stick with Yocto, you don't need to use -b or -recovery option, therefore you don't need xfstk.
The flashall.sh I'm using in the ubilinux build is the same one as from the Yocto 36.14 image.