Revert "Revert "Soong support for namespaces""

This mostly reverts commit 178d5fefc0cea9d0f031c0bdee125b9d960f32c3
and mostly reapplies change I6d3e52ef62c4cabe85b9a135a54de0e1a6aab29c .

Bug: 65683273
Test: build/soong/scripts/diff_build_graphs.sh \
      --products=aosp_arm \
      'build/blueprint:work^ build/soong:work^' \
      'build/blueprint:work build/soong:work'
      # and see that the only changes were:
      # 1. adding some new files
      # 2. changing some line numbers
Test: m -j nothing # which runs unit tests

Change-Id: I32baae00277a547fdcdd1c2219fe6625ee0e45d7
diff --git a/android/androidmk.go b/android/androidmk.go
index d88ba8f..12aa5fa 100644
--- a/android/androidmk.go
+++ b/android/androidmk.go
@@ -157,6 +157,12 @@
 		return nil
 	}
 
+	if !amod.commonProperties.NamespaceExportedToMake {
+		// TODO(jeffrygaston) do we want to validate that there are no modules being
+		// exported to Kati that depend on this module?
+		return nil
+	}
+
 	data := provider.AndroidMk()
 
 	if data.Include == "" {