[CONTRIB] Patch nnvcc to generate error when build the empty result (apache#1049)

Author: tqchen

README.md

@@ -1,4 +1,4 @@
-TVM: Tensor IR Stack for Deep Learning Systems
+<img src=https://raw.githubusercontent.com/tqchen/tvmlang.org/master/images/logo/tvm-logo-small.png width=128/> Tensor IR Stack for Deep Learning Systems
 ==============================================
 
 [![GitHub license](http://dmlc.github.io/img/apache2.svg)](./LICENSE)

python/tvm/contrib/nvcc.py

@@ -75,8 +75,11 @@ def compile_cuda(code,
         msg += py_str(out)
         raise RuntimeError(msg)
 
-    return bytearray(open(file_target, "rb").read())
-
+    data = bytearray(open(file_target, "rb").read())
+    if not data:
+        raise RuntimeError(
+            "Compilation error: empty result is generated")
+    return data
 
 def find_cuda_path():
     """Utility function to find cuda path