configure: use no-narrowing for cuda-llvm compilation

This fixes llvm compiler generating errors about narrowing conversion with
recent releases.

Signed-off-by: Timo Rothenpieler <timo@rothenpieler.org>

configure

@@ -6243,7 +6243,7 @@ fi
 if enabled cuda_nvcc; then
     nvccflags="$nvccflags -ptx"
 else
-    nvccflags="$nvccflags -S -nocudalib -nocudainc --cuda-device-only -include ${source_link}/compat/cuda/cuda_runtime.h"
+    nvccflags="$nvccflags -S -nocudalib -nocudainc --cuda-device-only -Wno-c++11-narrowing -include ${source_link}/compat/cuda/cuda_runtime.h"
     check_nvcc cuda_llvm
 fi