bp2build: framework for generating BazelTargetModules.

This CL creates the framework necessary for generating
BazelTargetModules from regular Soong Android modules.
BazelTargetModules are code-generated into Bazel targets in BUILD files.

See the follow-up CL for examples of creating filegroup/genrule
BazelTargetModules.

Test: GENERATE_BAZEL_FILES=true m nothing # creates out/soong/bp2build
with no BUILD files, because there are no BazelTargetModules in the
module graph.

Change-Id: I33a96365bd439043b13af6db9e439592e9983188

android/module.go

@@ -15,6 +15,7 @@
 package android
 
 import (
+	"android/soong/bazel"
 	"fmt"
 	"os"
 	"path"
@@ -491,6 +492,26 @@ type Module interface {
 	TransitivePackagingSpecs() []PackagingSpec
 }
 
+type BazelTargetModule interface {
+	Module
+
+	BazelTargetModuleProperties() *bazel.BazelTargetModuleProperties
+}
+
+func InitBazelTargetModule(module BazelTargetModule) {
+	module.AddProperties(module.BazelTargetModuleProperties())
+	InitAndroidModule(module)
+}
+
+type BazelTargetModuleBase struct {
+	ModuleBase
+	Properties bazel.BazelTargetModuleProperties
+}
+
+func (btmb *BazelTargetModuleBase) BazelTargetModuleProperties() *bazel.BazelTargetModuleProperties {
+	return &btmb.Properties
+}
+
 // Qualified id for a module
 type qualifiedModuleName struct {
 	// The package (i.e. directory) in which the module is defined, without trailing /
@@ -1069,6 +1090,9 @@ type ModuleBase struct {
 	archProperties          [][]interface{}
 	customizableProperties  []interface{}
 
+	// Properties specific to the Blueprint to BUILD migration.
+	bazelTargetModuleProperties bazel.BazelTargetModuleProperties
+
 	// Information about all the properties on the module that contains visibility rules that need
 	// checking.
 	visibilityPropertyInfo []visibilityProperty