Resolve prebuilt module explicitly for dex2oat tool dependencies.

func dex2oatPathFromDep(ctx android.ModuleContext) android.Path {

	dex2oatBin := dex2oatModuleName(ctx.Config())

	dex2oatModule := ctx.GetDirectDepWithTag(dex2oatBin, dex2oatDepTag)

	// Find the right dex2oat module, trying to follow PrebuiltDepTag from source

	// to prebuilt if there is one. We wouldn't have to do this if the

	// prebuilt_postdeps mutator that replaces source deps with prebuilt deps was

	// run after RegisterToolDeps above, but changing that leads to ordering

	// problems between mutators (RegisterToolDeps needs to run late to act on

	// final variants, while prebuilt_postdeps needs to run before many of the

	// PostDeps mutators, like the APEX mutators). Hence we need to dig out the

	// prebuilt explicitly here instead.

	var dex2oatModule android.Module

	ctx.WalkDeps(func(child, parent android.Module) bool {

		if parent == ctx.Module() && ctx.OtherModuleDependencyTag(child) == dex2oatDepTag {

			// Found the source module, or prebuilt module that has replaced the source.

			dex2oatModule = child

			if p, ok := child.(android.PrebuiltInterface); ok && p.Prebuilt() != nil {

				return false // If it's the prebuilt we're done.

			} else {

				return true // Recurse to check if the source has a prebuilt dependency.

			}

		}

		if parent == dex2oatModule && ctx.OtherModuleDependencyTag(child) == android.PrebuiltDepTag {

			if p, ok := child.(android.PrebuiltInterface); ok && p.Prebuilt() != nil && p.Prebuilt().UsePrebuilt() {

				dex2oatModule = child // Found a prebuilt that should be used.

			}

		}

		return false

	})

	if dex2oatModule == nil {

		// If this happens there's probably a missing call to AddToolDeps in DepsMutator.

		panic(fmt.Sprintf("Failed to lookup %s dependency", dex2oatBin))