vendor: update buildkit to f7bda278b7e2

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/github.com/containerd/platforms/defaults_unix.go

@@ -0,0 +1,40 @@
+//go:build !windows && !darwin && !freebsd
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package platforms
+
+import (
+	"runtime"
+
+	specs "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// DefaultSpec returns the current platform's default platform specification.
+func DefaultSpec() specs.Platform {
+	return specs.Platform{
+		OS:           runtime.GOOS,
+		Architecture: runtime.GOARCH,
+		// The Variant field will be empty if arch != ARM.
+		Variant: cpuVariant(),
+	}
+}
+
+// Default returns the default matcher for the platform.
+func Default() MatchComparer {
+	return Only(DefaultSpec())
+}