Some clarifications in preparation to automatically order linker dependencies

Test: Browse the code and determine whether it's easier to understand
Bug: 66260943
Change-Id: Ia3fdb8f38e83ad8225a72c8de2804db23a90ef9b

android/mutator.go

@@ -18,12 +18,13 @@ import (
 	"github.com/google/blueprint"
 )
 
-// Mutator phases:
-//   Pre-arch
-//   Arch
-//   Pre-deps
-//   Deps
-//   PostDeps
+// Phases:
+//   run Pre-arch mutators
+//   run archMutator
+//   run Pre-deps mutators
+//   run depsMutator
+//   run PostDeps mutators
+//   continue on to GenerateAndroidBuildActions
 
 func registerMutatorsToContext(ctx *blueprint.Context, mutators []*mutator) {
 	for _, t := range mutators {