Create an apex_contributions module type

This module type does not any build actions, but provides metadata about
the contributions of the mainline module to other mainline modules/
platform. One immediate use case for this metadata is source vs
prebuilts selection

Each mainline module can have more than 1 metadata modules. Static build
flags will be used to select the right one in trunk.bzl, next.bzl, ...

Bug: 308174923
Test: go build ./android
Change-Id: I5ead0c38fe64b78de08db1736d97a8ab7374d6d9

android/Android.bp

@@ -32,6 +32,7 @@ bootstrap_go_package {
     srcs: [
         "androidmk.go",
         "apex.go",
+        "apex_contributions.go",
         "api_domain.go",
         "api_levels.go",
         "arch.go",

android/apex_contributions.go

@@ -0,0 +1,67 @@
+// Copyright 2023 Google Inc. All rights reserved.
+//
+// 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 android
+
+import (
+	"github.com/google/blueprint/proptools"
+)
+
+func init() {
+	RegisterApexContributionsBuildComponents(InitRegistrationContext)
+}
+
+func RegisterApexContributionsBuildComponents(ctx RegistrationContext) {
+	ctx.RegisterModuleType("apex_contributions", apexContributionsFactory)
+}
+
+type apexContributions struct {
+	ModuleBase
+	properties contributionProps
+}
+
+type contributionProps struct {
+	// Name of the mainline module
+	Api_domain *string
+	// A list of module names that should be used when this contribution
+	// is selected via product_config
+	// The name should be explicit (foo or prebuilt_foo)
+	Contents []string
+}
+
+func (m *apexContributions) ApiDomain() string {
+	return proptools.String(m.properties.Api_domain)
+}
+
+func (m *apexContributions) Contents() []string {
+	return m.properties.Contents
+}
+
+// apex_contributions contains a list of module names (source or
+// prebuilt) belonging to the mainline module
+// An apex can have multiple apex_contributions modules
+// with different combinations of source or prebuilts, but only one can be
+// selected via product_config.
+func apexContributionsFactory() Module {
+	module := &apexContributions{}
+	module.AddProperties(&module.properties)
+	InitAndroidModule(module)
+	return module
+}
+
+// This module type does not have any build actions.
+// It provides metadata that is used in post-deps mutator phase for source vs
+// prebuilts selection.
+func (m *apexContributions) GenerateAndroidBuildActions(ctx ModuleContext) {
+}