Fix nondeterministic FullInstallPathInfo list

This list later shows up in the ninja file in soong-only builds, make
sure it's deterministic.

Test: Presubmits
Change-Id: Id121b8b95a543cd019f7c51f4121aa2c761f8a9f
diff --git a/filesystem/filesystem.go b/filesystem/filesystem.go
index f84993d..220a8c6 100644
--- a/filesystem/filesystem.go
+++ b/filesystem/filesystem.go
@@ -587,7 +587,8 @@
 	specs := f.gatherFilteredPackagingSpecs(ctx)
 
 	var fullInstallPaths []FullInstallPathInfo
-	for _, spec := range specs {
+	for _, specRel := range android.SortedKeys(specs) {
+		spec := specs[specRel]
 		fullInstallPaths = append(fullInstallPaths, FullInstallPathInfo{
 			FullInstallPath:     spec.FullInstallPath(),
 			RequiresFullInstall: spec.RequiresFullInstall(),