[yocto] Yocto update to Sumo with Multilib results in error in do_image_wic

[baisch at tau-tec.com]

After the update to Yocto 2.5 Sumo my genericx86 build doesn't work anymore. The problem seems to be with the Multilib feature. I need the 64 bit version of grub-efi so I've added this to my local.conf:

  require conf/multilib.conf
  MULTILIBS = "multilib:lib64"
  DEFAULTTUNE_virtclass-multilib-lib64 = "x86-64"
  IMAGE_INSTALL_append = " lib64-grub-efi"

With Sumo I get this error:

  image-dev-1.0-r0 do_image_wic: Error executing a python function in exec_python_func() autogenerated:

  […]

  Subprocess output:
  sed: can't read /workdir/poky/build-x86/tmp/work/genericx86-poky-linux/image-dev/1.0-r0/recipe-sysroot/usr/bin/crossscripts/x86_64-pokymllib64-linux-libtool: No such file or directory

The file `x86_64-pokymllib64-linux-libtool` is in `genericx86-pokymllib64-linux/image-dev/1.0-r0/lib64-recipe-sysroot/usr/bin/crossscripts/` (Note the difference: `lib64`). If I copy it over just to see what happens, another error pops up:

  ERROR: image-dev-1.0-r0 do_image_wic: Error executing a python function in exec_python_func() autogenerated:

  […]

  Exception: FileExistsError: [Errno 17] File exists: '/workdir/poky/build-x86/tmp/sysroots-components/x86_64/lib64-glibc/sysroot-providers/virtual_lib64-libc' -> '/workdir/poky/build-x86/tmp/work/genericx86-pokymllib64-linux/image-dev/1.0-r0/lib64-recipe-sysroot/sysroot-providers/virtual_lib64-libc'

  ERROR: image-dev-1.0-r0 do_image_wic: Function failed: extend_recipe_sysroot

Did something fundamentally change with Multilib in Sumo? I scanned the manual but it seems that I don't have to do anything different than before. https://www.yoctoproject.org/docs/2.5/mega-manual/mega-manual.html#using-multilib

When I comment the Multilib lines from the local.config it builds without errors.

For the full python stack trace see this post: https://stackoverflow.com/questions/50470148/yocto-update-to-sumo-with-multilib-results-in-error-in-do-image-wic