Merge pull request moby#42448 from thaJeztah/20.10_backport_update_buildkit

[20.10 backport] vendor: github.com/moby/buildkit v0.8.3-3-g244e8cde

Author: cpuguy83

vendor.conf

@@ -33,7 +33,7 @@ github.com/imdario/mergo                            1afb36080aec31e0d1528973ebe6
 golang.org/x/sync                                   cd5d95a43a6e21273425c7ae415d3df9ea832eeb
 
 # buildkit
-github.com/moby/buildkit                            9065b18ba4633c75862befca8188de4338d9f94a # v0.8.2
+github.com/moby/buildkit                            244e8cde639f71a05a1a2e0670bd88e0206ce55c # v0.8.3-3-g244e8cde
 github.com/tonistiigi/fsutil                        0834f99b7b85462efb69b4f571a4fa3ca7da5ac9
 github.com/tonistiigi/units                         6950e57a87eaf136bbe44ef2ec8e75b9e3569de2
 github.com/grpc-ecosystem/grpc-opentracing          8e809c8a86450a29b90dcc9efbf062d0fe6d9746