Handle build bake through bake, bake-files and bake-targets

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

test/Dockerfile-bake

@@ -0,0 +1,4 @@
+FROM alpine
+
+ARG name=world
+RUN echo "Hello ${name}!"

test/config.hcl

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+group "default" {
+  targets = ["db", "app"]
+}
+
+group "release" {
+  targets = ["db", "app-plus"]
+}
+
+target "db" {
+  context = "./test"
+  tags = ["docker.io/tonistiigi/db"]
+}
+
+target "app" {
+  context = "./test"
+  dockerfile = "Dockerfile-bake"
+  args = {
+    name = "foo"
+  }
+  tags = [
+    "localhost:5000/name/app:latest",
+    "localhost:5000/name/app:1.0.0"
+  ]
+}
+
+target "cross" {
+  platforms = [
+    "linux/amd64",
+    "linux/arm64",
+    "linux/386"
+  ]
+}
+
+target "app-plus" {
+  inherits = ["app", "cross"]
+  args = {
+    IAMPLUS = "true"
+  }
+}