vulkan-samples: add lfs=0 to SRC_URI to avoid git smudge errors in do_unpack

vulkan-samples: add lfs=0 to SRC_URI to avoid git smudge errors in do_unpack

* we don't need other_lib/ios/Debug-iphoneos/libSDL2.a from
  https://github.com/KhronosGroup/KTX-Software.git so we can explicitly
  disable LFS here to avoid do_unpack error, bitbake will then use
  GIT_LFS_SKIP_SMUDGE=1 to override smudge setting in gitconfig,
  otherwise we would need bitbake patch to fetch LFS objects from the
  submodules as well

* do_fetch won't fetch LFS objects without explicitly requesting lfs in SRC_URI
  then do_unpack might run git smudge when enabled in .gitconfig (or /etc/gitconfig) with:

[filter "lfs"]
       smudge = git-lfs smudge -- %f
       process = git-lfs filter-process
       required = true
       clean = git-lfs clean -- %f

  and do_unpack fails as in:
  http://errors.yoctoproject.org/Errors/Details/672888/

The default /etc/gitconfig in ubuntu has this added automatically by
git-lfs postinst:

  root@ljama:~# rm /etc/gitconfig
  root@ljama:~# git lfs install --skip-repo --system
  Git LFS initialized.
  root@ljama:~# cat /etc/gitconfig
  [filter "lfs"]
        clean = git-lfs clean -- %f
        smudge = git-lfs smudge -- %f
        process = git-lfs filter-process
        required = true
  root@ljama:~# cat /var/lib/dpkg/info/git-lfs.postinst

  set -e

  # Set up /etc/gitconfig for git-lfs. The --skip-repo option prevents failure if
  # / is a Git repository with existing non-git-lfs hooks.

  git lfs install --skip-repo --system > /dev/null 2>&1

according to
https://changelogs.ubuntu.com/changelogs/pool/universe/g/git-lfs/git-lfs_3.0.2-1/changelog
it was added in:

git-lfs (2.6.0-1) unstable; urgency=medium

  * New upstream release
  * Bump standards version to 4.2.1
  * Add postinst/prerm to set up/remove git-lfs gitconfig

FWIW: vulkan-samples still fail to build with DEBUG_BUILD enabled:
http://errors.yoctoproject.org/Errors/Details/672892/

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>