Adapt upstream API change from r319082.

PiperOrigin-RevId: 177173806

Author: tensorflower-gardener

tensorflow/compiler/xla/service/gpu/llvm_gpu_backend/gpu_backend_lib.cc

@@ -34,7 +34,7 @@ limitations under the License.
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/Bitcode/BitcodeWriter.h"
-#include "llvm/CodeGen/CommandFlags.h"
+#include "llvm/CodeGen/CommandFlags.def"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Module.h"