make grpc_csharp_ext compile and install independently from the grpc and gpr libraries
diff --git a/build.json b/build.json
index a092964..c552228 100644
--- a/build.json
+++ b/build.json
@@ -345,7 +345,7 @@
     {
       "name": "grpc_csharp_ext",
       "build": "all",
-      "language": "c",
+      "language": "csharp",
       "src": [
         "src/csharp/ext/grpc_csharp_ext.c"
       ],