Fix prebuilt selection logic for cc_prebuilt_library_headers.

Unlike other prebuilt modules it doesn't have a srcs property of any
kind, so android.Prebuilt cannot defer to the source module just
because its srcsSupplier would return nil.

Test: m nothing
Bug: 202192894
Change-Id: Iafcf165569bad6eae37820cf71aa0fcacb720e02
diff --git a/cc/library_headers.go b/cc/library_headers.go
index ede6ab3..141a2a5 100644
--- a/cc/library_headers.go
+++ b/cc/library_headers.go
@@ -102,7 +102,7 @@
 
 // cc_prebuilt_library_headers is a prebuilt version of cc_library_headers
 func prebuiltLibraryHeaderFactory() android.Module {
-	module, library := NewPrebuiltLibrary(android.HostAndDeviceSupported)
+	module, library := NewPrebuiltLibrary(android.HostAndDeviceSupported, "")
 	library.HeaderOnly()
 	return module.Init()
 }