Record the inputs of a build's source fingerprint in its build record (issue 1215)

internal/builder/source.go

@@ -278,6 +278,15 @@ func (s *sourceInputs) inputs() delivery.SourceInputs {
 	}
 }
 
+// resultInputs are the inputs a build's result records; nil for a build with no inputs to speak of.
+func resultInputs(s *sourceInputs) *delivery.SourceInputs {
+	if s == nil {
+		return nil
+	}
+	in := s.inputs()
+	return &in
+}
+
 // fingerprint is the build's source fingerprint, or empty when the source does not pin the build.
 func (s *sourceInputs) fingerprint() string {
 	if s == nil {