message: Add kernel info for zero kernels
diff: @@ -179,10 +179,12 @@ boost::future<std::unique_ptr<hal::Library>> Compiler::Build(const context::Cont
  for (const auto& ki : kernel_info) {
  context::Activity kbuild{activity.ctx(), "tile::hal::opencl::BuildKernel"};
  - if (ki.ktype == lang::KernelType::kZero) {
  - continue;
  - }
  + proto::KernelInfo kinfo;
  + kinfo.set_kname(ki.kname);
  + if (ki.ktype == lang::KernelType::kZero) {
  + kinfo.set_src("// Builtin zero kernel");
  + } else {
  Emit ocl{cl_khr_fp16, cl_khr_fp64};
  ocl.Visit(*ki.kfunc);
  std::string src = ki.comments + ocl.str();
  @@ -209,9 +211,9 @@ boost::future<std::unique_ptr<hal::Library>> Compiler::Build(const context::Cont
  code << src;
  code << "\n\n";
  - proto::KernelInfo kinfo;
  - kinfo.set_kname(ki.kname);
  kinfo.set_src(src);
  + }
  +
  *(kinfo.mutable_kinfo()) = ki.info;
  kbuild.AddMetadata(kinfo);
  