Make no-cgo build work without source changes

webp.go

@@ -0,0 +1,14 @@
+// +build cgo
+
+package main
+
+import (
+	"image"
+	"io"
+
+	"github.com/chai2010/webp"
+)
+
+func decodeWebp(r io.Reader) (image.Image, error) {
+	return webp.Decode(r)
+}