Remove LOCAL_CPP_EXTENSION during Android.mk translation

LOCAL_CPP_EXTENSION is unnecesary in soong, it can accept files
with .cc or .cpp extension.

Change-Id: I64cb37f199e25f1fed7e53144f85e52ba616529a
diff --git a/androidmk/cmd/androidmk/android.go b/androidmk/cmd/androidmk/android.go
index 48905a7..5544dfd 100644
--- a/androidmk/cmd/androidmk/android.go
+++ b/androidmk/cmd/androidmk/android.go
@@ -56,6 +56,10 @@
 	"LOCAL_RTTI_FLAG":               "rtti",
 }
 
+var deleteProperties = map[string]struct{}{
+	"LOCAL_CPP_EXTENSION": struct{}{},
+}
+
 var propertySuffixes = []struct {
 	suffix string
 	class  string
diff --git a/androidmk/cmd/androidmk/androidmk.go b/androidmk/cmd/androidmk/androidmk.go
index 6695181..fd31a13 100644
--- a/androidmk/cmd/androidmk/androidmk.go
+++ b/androidmk/cmd/androidmk/androidmk.go
@@ -241,6 +241,8 @@
 		err = setVariable(file, assignment.Value, assignment.Type == "+=", prop, bpparser.List, true, class, suffix)
 	} else if prop, ok := boolProperties[name]; ok {
 		err = setVariable(file, assignment.Value, assignment.Type == "+=", prop, bpparser.Bool, true, class, suffix)
+	} else if _, ok := deleteProperties[name]; ok {
+		return
 	} else {
 		if name == "LOCAL_PATH" {
 			// Nothing to do, except maybe avoid the "./" in paths?