[19.03] vendor: moby/buildkit v0.6.4-26-ga1e4f48e

full diff: moby/buildkit@4cb720e...a1e4f48

Brings in the cherry-picks from moby/buildkit#1596 and moby/buildkit#1598 :

- Add --force flag in git fetch command
- Fix socket handling during copy (Treat unix sockets as regular files)
- Remotecache: Only visit each item once when walking results.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Upstream-commit: 765245d54b0aad21795e01f504bd1078552bef4a
Component: engine

Author: thaJeztah

components/engine/vendor.conf

@@ -26,7 +26,7 @@ github.com/imdario/mergo                            7c29201646fa3de8506f70121347
 golang.org/x/sync                                   e225da77a7e68af35c70ccbf71af2b83e6acac3c
 
 # buildkit
-github.com/moby/buildkit                            4cb720ef6483b43020c9037726de47353ac8ad9b # v0.6.4-20-g4cb720ef
+github.com/moby/buildkit                            a1e4f48e712360e6292819e55285e1bbacce99d4 # v0.6.4-26-ga1e4f48e
 github.com/tonistiigi/fsutil                        6c909ab392c173a4264ae1bfcbc0450b9aac0c7d
 github.com/grpc-ecosystem/grpc-opentracing          8e809c8a86450a29b90dcc9efbf062d0fe6d9746
 github.com/opentracing/opentracing-go               1361b9cd60be79c4c3a7fa9841b3c132e40066a7