Move product_packages.txt to soong

Needed for soong-only builds.

Bug: 383892968
Test: Presubmits
Change-Id: Ibc214f489d97b2eb2ff29e454af3bf1ae025b0d2
diff --git a/android/paths.go b/android/paths.go
index 94f00ad..9a7dcbc 100644
--- a/android/paths.go
+++ b/android/paths.go
@@ -1353,7 +1353,7 @@
 
 // PathForArbitraryOutput creates a path for the given components. Unlike PathForOutput,
 // the path is relative to the root of the output folder, not the out/soong folder.
-func PathForArbitraryOutput(ctx PathContext, pathComponents ...string) Path {
+func PathForArbitraryOutput(ctx PathContext, pathComponents ...string) WritablePath {
 	path, err := validatePath(pathComponents...)
 	if err != nil {
 		reportPathError(ctx, err)