bake: fix undefined output property

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

__tests__/buildx/bake.test.ts

@@ -31,9 +31,14 @@ describe('parseDefinitions', () => {
   // prettier-ignore
   test.each([
     [
-      [path.join(fixturesDir, 'bake.hcl')],
+      [path.join(fixturesDir, 'bake-01.hcl')],
       ['validate'],
-      path.join(fixturesDir, 'bake-validate.json')
+      path.join(fixturesDir, 'bake-01-validate.json')
+    ],
+    [
+      [path.join(fixturesDir, 'bake-02.hcl')],
+      ['build'],
+      path.join(fixturesDir, 'bake-02-build.json')
     ]
   ])('given %p', async (sources: string[], targets: string[], out: string) => {
     const bake = new Bake();
@@ -57,6 +62,16 @@ describe('hasLocalExporter', () => {
       },
       false
     ],
+    [
+      {
+        "target": {
+          "build": {
+            "target": "build"
+          },
+        }
+      },
+      false
+    ],
     [
       {
         "target": {

__tests__/fixtures/bake-02-build.json

@@ -0,0 +1,20 @@
+{
+  "group": {
+    "default": {
+      "targets": [
+        "build"
+      ]
+    }
+  },
+  "target": {
+    "build": {
+      "context": ".",
+      "dockerfile": "Dockerfile",
+      "args": {
+        "BUILDKIT_CONTEXT_KEEP_GIT_DIR": "1",
+        "GO_VERSION": "1.20"
+      },
+      "target": "build"
+    }
+  }
+}

__tests__/fixtures/bake-02.hcl

@@ -0,0 +1,33 @@
+// Copyright 2023 actions-toolkit 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.
+
+variable "GO_VERSION" {
+  default = "1.20"
+}
+
+target "_common" {
+  args = {
+    GO_VERSION = GO_VERSION
+    BUILDKIT_CONTEXT_KEEP_GIT_DIR = 1
+  }
+}
+
+group "default" {
+  targets = ["build"]
+}
+
+target "build" {
+  inherits = ["_common"]
+  target = "build"
+}