Add PrebuiltNameFromSource

Bug: 177892522
Test: m nothing
Change-Id: I45274836d59adbd6b2a2a848705b189398f1e766
diff --git a/android/prebuilt.go b/android/prebuilt.go
index b43d238..8176299 100644
--- a/android/prebuilt.go
+++ b/android/prebuilt.go
@@ -82,6 +82,12 @@
 }
 
 func (p *Prebuilt) Name(name string) string {
+	return PrebuiltNameFromSource(name)
+}
+
+// PrebuiltNameFromSource returns the result of prepending the "prebuilt_" prefix to the supplied
+// name.
+func PrebuiltNameFromSource(name string) string {
 	return "prebuilt_" + name
 }