check-flagged-apis: add new CLI to verify @FlaggedApi APIs

Add a new CLI to verify that the build artifacts contain the right set
of @FlaggedApi APIs, based on the value of the corresponding aconfig
flag.

This CLI will act as an end-to-end test of Soong and metalava.

This CL only adds the project scaffolding; later CLs will add the
implementation.

Bug: 334870672
Test: m check-flagged-apis && check-flagged-apis
Change-Id: Ib00653f2a549217da2b0058867c711f35efd5760

PREUPLOAD.cfg

@@ -1,2 +1,5 @@
 [Hook Scripts]
 do_not_use_DO_NOT_MERGE = ${REPO_ROOT}/build/soong/scripts/check_do_not_merge.sh ${PREUPLOAD_COMMIT}
+
+[Builtin Hooks]
+ktfmt = true

tools/check-flagged-apis/Android.bp

@@ -0,0 +1,25 @@
+// Copyright (C) 2024 The Android Open Source Project
+//
+// 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 {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+java_binary_host {
+    name: "check-flagged-apis",
+    srcs: [
+        "src/**/*.kt",
+    ],
+    main_class: "com.android.checkflaggedapis.Main",
+}

tools/check-flagged-apis/OWNERS

@@ -0,0 +1,4 @@
+amhk@google.com
+gurpreetgs@google.com
+michaelwr@google.com
+paulduffin@google.com

tools/check-flagged-apis/src/com/android/checkflaggedapis/Main.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * 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.
+ */
+@file:JvmName("Main")
+
+package com.android.checkflaggedapis
+
+fun main() = println("hello world")