Merge pull request moby#820 from AkihiroSuda/runc20190211

bump up runc

Merge pull request moby#747 from Quasilyte/patch-1

snapshot: fix impossible condition

Merge pull request moby#747 from Quasilyte/patch-1

snapshot: fix impossible condition

Merge pull request moby#730 from tonistiigi/no-cache-fix

buildctl: fix frontends ignore-cache setting

Merge pull request moby#716 from tonistiigi/copy-source

dockerfile: update copy source repo

Merge pull request moby#716 from tonistiigi/copy-source

dockerfile: update copy source repo

Merge pull request moby#712 from tonistiigi/clean-readlink

contenthash: clean readlink value

Merge pull request moby#708 from AkihiroSuda/cli-no-cache

buildctl: support --no-cache for Dockerfile frontend

Merge pull request moby#708 from AkihiroSuda/cli-no-cache

buildctl: support --no-cache for Dockerfile frontend

Merge pull request moby#693 from tonistiigi/containerd-debug-sock

testutil: use different containerd debug sock