Fixing a test case which was failing the MSVC build bots. When -std isn't...

Fixing a test case which was failing the MSVC build bots. When -std isn't specified with an MSVC build, it defaults to -std=c++11, which overrides the -x cuda option. In turn, this causes all CUDA language option checks to fail.

This fix is possibly temporary while we determine whether -x cuda should be considered along with -std=c++11 when setting language options.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209808 91177308-0d34-0410-b5e6-96231b3b80d8

test/Index/attributes-cuda.cu

-// RUN: c-index-test -test-load-source all -x cuda %s | FileCheck %s
+// RUN: c-index-test -test-load-source all -x cuda -std=cuda %s | FileCheck %s
 
 __attribute__((device)) void f_device();
 __attribute__((global)) void f_global();