Fix compile warning in search.cu

[davidwendt]

Compile warning introduced with merge of PR #10802

10 warnings like this:
12:43:23 $SRC_DIR/cpp/src/search/search.cu(108): warning #177-D: parameter "args" was declared but never referenced
12:43:23           detected during instantiation of function "lambda [](auto &&...)->auto [with <auto-1>=<rmm::exec_policy, const
thrust::counting_iterator<cudf::size_type, thrust::use_default, thrust::use_default, thrust::use_default> &, 
thrust::counting_iterator<cudf::size_type, thrust::use_default, thrust::use_default, thrust::use_default>, const 
thrust::counting_iterator<cudf::size_type, thrust::use_default, thrust::use_default, thrust::use_default> &, 
thrust::counting_iterator<cudf::size_type, thrust::use_default, thrust::use_default, thrust::use_default>, cudf::size_type *const &, 
const cudf::row_lexicographic_comparator<cudf::nullate::DYNAMIC> &>]" 
12:43:23 (121): here

Line 108 has a lambda refactoring that seems to confuse the compiler.

  auto const do_search = [find_first](auto&&... args) {
    if (find_first) {
      thrust::lower_bound(std::forward<decltype(args)>(args)...);
    } else {
      thrust::upper_bound(std::forward<decltype(args)>(args)...);
    }
  };
  do_search(rmm::exec_policy(stream),
            count_it,  count_it + haystack.num_rows(), count_it, count_it + needles.num_rows(),
            out_it, comp);

The warning is wrong and the compiler generates the correct code so this is likely a compiler bug.

This PR fixes the warning by replacing the lambda with an if statement.

[ttnghia]

Oh I'm sorry about this. I saw the warning but ignored it as I thought this is a compiler bug and it will be fixed on the cuda sdk side.

[codecov]

Codecov Report

Merging #10827 (f44ee3b) into branch-22.06 (8d861ce) will decrease coverage by 0.09%.
The diff coverage is 94.84%.

❗ Current head f44ee3b differs from pull request most recent head 5c53edf. Consider uploading reports for the commit 5c53edf to get more accurate results

@@               Coverage Diff                @@
##           branch-22.06   #10827      +/-   ##
================================================
- Coverage         86.40%   86.31%   -0.10%     
================================================
  Files               143      144       +1     
  Lines             22448    22648     +200     
================================================
+ Hits              19396    19548     +152     
- Misses             3052     3100      +48     

Impacted Files	Coverage Δ
python/cudf/cudf/core/column/string.py	88.78% <ø> (-0.31%)	⬇️
python/cudf/cudf/core/frame.py	93.41% <ø> (ø)
python/cudf/cudf/core/indexed_frame.py	91.70% <ø> (ø)
python/cudf/cudf/io/__init__.py	100.00% <ø> (ø)
python/cudf/cudf/testing/testing.py	81.81% <50.00%> (+0.12%)	⬆️
python/cudf/cudf/io/parquet.py	90.83% <86.60%> (-1.87%)	⬇️
python/cudf/cudf/core/index.py	92.06% <88.88%> (-0.25%)	⬇️
python/cudf/cudf/core/scalar.py	89.01% <90.90%> (-0.31%)	⬇️
python/cudf/cudf/core/dataframe.py	93.78% <96.36%> (+0.08%)	⬆️
python/cudf/cudf/__init__.py	90.69% <100.00%> (+0.22%)	⬆️
... and 29 more

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[davidwendt]

@gpucibot merge