[llvm] [NFC] LLVM reduce: remove unused variable (PR #133584)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-ubuntu-fast` running on `sie-linux-worker` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/21552

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (build-unified-tree) failure: build (failure)
0.012 [129/3/1] Building CXX object tools/llvm-config/CMakeFiles/llvm-config.dir/llvm-config.cpp.o
0.019 [128/3/2] Generating VCSRevision.h
0.028 [124/6/3] Generating VCSVersion.inc
0.050 [123/6/4] Linking CXX executable bin/llvm-config
0.563 [123/5/5] Building CXX object tools/clang/lib/Basic/CMakeFiles/obj.clangBasic.dir/Version.cpp.o
2.169 [123/4/6] Building CXX object tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o
FAILED: tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /usr/bin/g++ -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_STATIC -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/llvm-reduce -I/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/tools/llvm-reduce -I/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/include -I/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -std=c++17 -MD -MT tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o -MF tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o.d -o tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o -c /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp: In function ‘void replaceFunctionCalls(llvm::Function*, llvm::Function*)’:
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp:112:29: error: ‘void llvm::FPMathOperator::setFastMathFlags(llvm::FastMathFlags)’ is private within this context
  112 |       FPOp->setFastMathFlags(CI->getFastMathFlags());
      |       ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
In file included from /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp:17:
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include/llvm/IR/Operator.h:264:8: note: declared private here
  264 |   void setFastMathFlags(FastMathFlags FMF) {
      |        ^~~~~~~~~~~~~~~~
2.330 [123/3/7] Building CXX object lib/Object/CMakeFiles/LLVMObject.dir/IRSymtab.cpp.o
10.963 [123/2/8] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/AsmPrinter.cpp.o
11.896 [123/1/9] Building CXX object lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/133584