vendor: update buildkit to v0.8

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

vendor/github.com/tonistiigi/fsutil/docker-bake.hcl

@@ -0,0 +1,58 @@
+variable "GO_VERSION" {
+  default = "1.13"
+}
+
+group "default" {
+  targets = ["build"]
+}
+
+target "build" {
+  args = {
+    GO_VERSION = "${GO_VERSION}"
+  }
+}
+
+group "test" {
+  targets = ["test-root", "test-noroot"]
+}
+
+target "test-root" {
+  inherits = ["build"]
+  target = "test"
+}
+
+target "test-noroot" {
+  inherits = ["build"]
+  target = "test-noroot"
+}
+
+target "lint" {
+  dockerfile = "./hack/dockerfiles/lint.Dockerfile"
+}
+
+target "validate-gomod" {
+  dockerfile = "./hack/dockerfiles/gomod.Dockerfile"
+  target = "validate"
+}
+
+target "gomod" {
+  inherits = ["validate-gomod"]
+  output = ["."]
+  target = "update"
+}
+
+target "validate-shfmt" {
+  dockerfile = "./hack/dockerfiles/shfmt.Dockerfile"
+  target = "validate"
+}
+
+target "shfmt" {
+  inherits = ["validate-shfmt"]
+  output = ["."]
+  target = "update"
+}
+
+target "cross" {
+  inherits = ["build"]
+  platforms = ["linux/amd64", "linux/arm64", "linux/arm", "linux/ppc64le", "linux/s390x"]
+}