During device-side CUDA compilation clang currently complains about
all TLS variables, regardless of whether they are __host__ or
__device__.

This patch suppresses "TLS unsupported" errors for host variables
during device compilation and for device variables during host
compilation.

Differential Revision: http://reviews.llvm.org/D9269

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@235907 91177308-0d34-0410-b5e6-96231b3b80d8