Update import paths for changes to blueprint

Blueprint has been modified to include a canonical import path,
update soong to match.

Change-Id: If29d31afbf3bf2e6364961a66456fa5f8f738455
diff --git a/common/paths.go b/common/paths.go
index 91b8f99..bc75ea5 100644
--- a/common/paths.go
+++ b/common/paths.go
@@ -17,7 +17,7 @@
 import (
 	"path/filepath"
 
-	"blueprint"
+	"github.com/google/blueprint"
 )
 
 type Config interface {