Refactor cc/sabi.go

* Rename `vndk_deps` mutator to `sabi_deps` to better reflect its
  purpose.
* Eliminate duplication of ABI dump generation logic. sabiDepsMutator
  should call libraryDecorator.shouldCreateSourceAbiDump() to determine
  if a module needs to be marked with CreateSAbiDumps.
* Non-VNDK libraries that are opt-in to ABI check would have their
  dependencies correctly marked with CreateSAbiDumps.
* Refactor some lines to idiomatic syntax.
* Add comment strings.

Bug: 145608479
Bug: 173492236
Test: TH presubmit
Change-Id: I99e97787bdf2a4f0c970809161b64aa668ff3d1a

cc/cc.go

@@ -79,7 +79,6 @@ func RegisterCCBuildComponents(ctx android.RegistrationContext) {
 		ctx.BottomUp("sanitize_runtime", sanitizerRuntimeMutator).Parallel()
 
 		ctx.BottomUp("coverage", coverageMutator).Parallel()
-		ctx.TopDown("vndk_deps", sabiDepsMutator)
 
 		ctx.TopDown("lto_deps", ltoDepsMutator)
 		ctx.BottomUp("lto", ltoMutator).Parallel()
@@ -88,6 +87,11 @@ func RegisterCCBuildComponents(ctx android.RegistrationContext) {
 		ctx.TopDown("double_loadable", checkDoubleLoadableLibraries).Parallel()
 	})
 
+	ctx.FinalDepsMutators(func(ctx android.RegisterMutatorsContext) {
+		// sabi mutator needs to be run after apex mutator finishes.
+		ctx.TopDown("sabi_deps", sabiDepsMutator)
+	})
+
 	ctx.RegisterSingletonType("kythe_extract_all", kytheExtractAllFactory)
 }