Support multiple outputs for genrule

The underlying code to expose outputs to other modules has suppported
this already for gensrcs (which runs the command multiple times to
create multiple outputs). This allows a genrule to run a command once,
and output multiple files.

Bug: 31742855
Test: Add multi-output genrule; Inspect build.ninja
Change-Id: I72054cc39c0d0e3e44feebba72005e5af1a1709a

genrule/genrule.go

@@ -85,7 +85,7 @@ type taskFunc func(ctx android.ModuleContext) []generateTask
 
 type generateTask struct {
 	in  android.Paths
-	out android.ModuleGenPath
+	out android.WritablePaths
 }
 
 func (g *generator) GeneratedSourceFiles() android.Paths {
@@ -167,7 +167,7 @@ func (g *generator) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 func (g *generator) generateSourceFile(ctx android.ModuleContext, task generateTask, tool string) {
 	ctx.ModuleBuild(pctx, android.ModuleBuildParams{
 		Rule:      g.rule,
-		Output:    task.out,
+		Outputs:   task.out,
 		Inputs:    task.in,
 		Implicits: g.deps,
 		Args: map[string]string{
@@ -175,7 +175,9 @@ func (g *generator) generateSourceFile(ctx android.ModuleContext, task generateT
 		},
 	})
 
-	g.outputFiles = append(g.outputFiles, task.out)
+	for _, outputFile := range task.out {
+		g.outputFiles = append(g.outputFiles, outputFile)
+	}
 }
 
 func generatorFactory(tasks taskFunc, props ...interface{}) (blueprint.Module, []interface{}) {
@@ -197,7 +199,7 @@ func GenSrcsFactory() (blueprint.Module, []interface{}) {
 		for _, in := range srcFiles {
 			tasks = append(tasks, generateTask{
 				in:  android.Paths{in},
-				out: android.GenPathWithExt(ctx, in, properties.Output_extension),
+				out: android.WritablePaths{android.GenPathWithExt(ctx, in, properties.Output_extension)},
 			})
 		}
 		return tasks
@@ -218,10 +220,14 @@ func GenRuleFactory() (blueprint.Module, []interface{}) {
 	properties := &genRuleProperties{}
 
 	tasks := func(ctx android.ModuleContext) []generateTask {
+		outs := make(android.WritablePaths, len(properties.Out))
+		for i, out := range properties.Out {
+			outs[i] = android.PathForModuleGen(ctx, out)
+		}
 		return []generateTask{
 			{
 				in:  ctx.ExpandSources(properties.Srcs, nil),
-				out: android.PathForModuleGen(ctx, properties.Out),
+				out: outs,
 			},
 		}
 	}
@@ -233,6 +239,6 @@ type genRuleProperties struct {
 	// list of input files
 	Srcs []string
 
-	// name of the output file that will be generated
-	Out string
+	// names of the output files that will be generated
+	Out []string
 }