Fix warnings in release build.

This fixes a couple of Clang warnings in release builds of LLVM:

* Missing return in ISelLowering
* Unused variable in NVPTXutil.cpp

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156216 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/NVPTX/NVPTXutil.cpp b/lib/Target/NVPTX/NVPTXutil.cpp
index de311d2..6a0e532 100644
--- a/lib/Target/NVPTX/NVPTXutil.cpp
+++ b/lib/Target/NVPTX/NVPTXutil.cpp
@@ -75,6 +75,7 @@
 
   int retval = encode_leb128(temp64.x, &nbytes, encoded, 16);
 
+  (void)retval;
   assert(retval == 0 &&
          "Encoding to leb128 failed");