Use R.txt files from aar files directly

Use the R.txt files from aar imports directly instead of recreating
one using aapt2 from the embedded resources.  Fixes an issue with
com.google.android.material where the jar was referencing
com.google.android.material.R.attr.theme, aapt2 was not producing
"int attr theme 0x0" in R.txt, but the aar's R.txt had it.

Bug: 294256649
Test: builds
Change-Id: Ibe1e5535a75eed59f3b8dbbc12eff9c07af51d37
diff --git a/java/aar.go b/java/aar.go
index f61fc83..79c552d 100644
--- a/java/aar.go
+++ b/java/aar.go
@@ -1136,7 +1136,7 @@
 	extractedAARDir := android.PathForModuleOut(ctx, "aar")
 	a.classpathFile = extractedAARDir.Join(ctx, "classes-combined.jar")
 	a.manifest = extractedAARDir.Join(ctx, "AndroidManifest.xml")
-	aarRTxt := extractedAARDir.Join(ctx, "R.txt")
+	a.rTxt = extractedAARDir.Join(ctx, "R.txt")
 	a.assetsPackage = android.PathForModuleOut(ctx, "assets.zip")
 	a.proguardFlags = extractedAARDir.Join(ctx, "proguard.txt")
 	android.SetProvider(ctx, ProguardSpecInfoProvider, ProguardSpecInfo{
@@ -1150,7 +1150,7 @@
 	ctx.Build(pctx, android.BuildParams{
 		Rule:        unzipAAR,
 		Input:       a.aarPath,
-		Outputs:     android.WritablePaths{a.classpathFile, a.proguardFlags, a.manifest, a.assetsPackage, aarRTxt},
+		Outputs:     android.WritablePaths{a.classpathFile, a.proguardFlags, a.manifest, a.assetsPackage, a.rTxt},
 		Description: "unzip AAR",
 		Args: map[string]string{
 			"outDir":             extractedAARDir.String(),
@@ -1168,7 +1168,7 @@
 
 	a.exportPackage = android.PathForModuleOut(ctx, "package-res.apk")
 	proguardOptionsFile := android.PathForModuleGen(ctx, "proguard.options")
-	a.rTxt = android.PathForModuleOut(ctx, "R.txt")
+	aaptRTxt := android.PathForModuleOut(ctx, "R.txt")
 	a.extraAaptPackagesFile = android.PathForModuleOut(ctx, "extra_packages")
 
 	var linkDeps android.Paths
@@ -1204,7 +1204,7 @@
 	}
 
 	transitiveAssets := android.ReverseSliceInPlace(staticDeps.assets())
-	aapt2Link(ctx, a.exportPackage, nil, proguardOptionsFile, a.rTxt,
+	aapt2Link(ctx, a.exportPackage, nil, proguardOptionsFile, aaptRTxt,
 		linkFlags, linkDeps, nil, overlayRes, transitiveAssets, nil, nil)
 
 	a.rJar = android.PathForModuleOut(ctx, "busybox/R.jar")