Fix a warning building on my machine, NFC. warning: unused function 'compilePtxToCubinForTesting'

[lattner]

Summary

Also eliminate the redunant anon namespace around the already static function.

[rriddle]

Ooops, thanks. I shouldn't submit late at night.

mlir/test/lib/Transforms/TestConvertGPUKernelToCubin.cpp

 //===- TestConvertGPUKernelToCubin.cpp - Test gpu kernel cubin lowering ---===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Conversion/GPUToCUDA/GPUToCUDAPass.h"
 #include "mlir/Pass/Pass.h"
 #include "mlir/Pass/PassManager.h"
-
 using namespace mlir;
 
-namespace {
+#if MLIR_CUDA_CONVERSIONS_ENABLED
 static OwnedCubin compilePtxToCubinForTesting(const std::string &, Location,
                                               StringRef) {
   const char data[] = "CUBIN";
   return std::make_unique<std::vector<char>>(data, data + sizeof(data) - 1);
 }
-} // end anonymous namespace
 
-#if MLIR_CUDA_CONVERSIONS_ENABLED
 namespace mlir {
 void registerTestConvertGPUKernelToCubinPass() {
   PassPipelineRegistration<>("test-kernel-to-cubin",
                              "Convert all kernel functions to CUDA cubin blobs",
                              [](OpPassManager &pm) {
                                pm.addPass(createConvertGPUKernelToCubinPass(
                                    compilePtxToCubinForTesting));
                              });
 }
 } // namespace mlir
 #endif