Add exported_java_aconfig_library

Add a rule to generate a JAR file containing code for all aconfig flags
in all packages. This is intended for apps compiled outside the
platform.

Also add a rule to include the new JAR file among the SDK artifacts.

Note: a future CL will refine the aconfig command line options used, or
filter the aconfig output: right now the JAR really contains *all*
flags; we want it to include only *exported* flags.

Bug: 311151343
Test: m sdk dist # manually verify that this generates $(gettop)/out/dist/android-flags.jar
Change-Id: I73481a9f723a0e5487cfcd2ee697873ecc4e8275

aconfig/init.go

@@ -67,6 +67,20 @@ var (
 			Command:     `${aconfig} dump --dedup --format protobuf --out $out $flags`,
 			CommandDeps: []string{"${aconfig}"},
 		}, "flags")
+	// For exported_java_aconfig_library: Generate a JAR from all
+	// java_aconfig_libraries to be consumed by apps built outside the
+	// platform
+	exportedJavaRule = pctx.AndroidStaticRule("exported_java_aconfig_library",
+		blueprint.RuleParams{
+			Command: `rm -rf ${out}.tmp` +
+				`&& for cache in ${cache_files}; do ${aconfig} create-java-lib --cache $$cache --out ${out}.tmp; done` +
+				`&& $soong_zip -write_if_changed -jar -o ${out} -C ${out}.tmp -D ${out}.tmp` +
+				`&& rm -rf ${out}.tmp`,
+			CommandDeps: []string{
+				"$aconfig",
+				"$soong_zip",
+			},
+		}, "cache_files")
 )
 
 func init() {
@@ -80,4 +94,5 @@ func RegisterBuildComponents(ctx android.RegistrationContext) {
 	ctx.RegisterModuleType("aconfig_values", ValuesFactory)
 	ctx.RegisterModuleType("aconfig_value_set", ValueSetFactory)
 	ctx.RegisterParallelSingletonType("all_aconfig_declarations", AllAconfigDeclarationsFactory)
+	ctx.RegisterParallelSingletonType("exported_java_aconfig_library", ExportedJavaDeclarationsLibraryFactory)
 }