[clang] [llvm] [CoroSplit] Erase trivially dead allocas after spilling (PR #189295)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-flang-rhel-clang` running on `ppc64le-flang-rhel-test` while building `clang,llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/45549

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

```
Step 5 (build-unified-tree) failure: build (failure) (timed out)
...
103.613 [4/11/126] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/descriptor-io.cpp.o
127.017 [4/10/127] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/reduction.cpp.o
185.072 [4/9/128] Building CXX object third-party/runtimes_gtest/CMakeFiles/runtimes_gtest.dir/googletest/src/gtest-all.cc.o
186.178 [3/9/129] Linking CXX static library /home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/build/lib/libruntimes_gtest.a
187.054 [1/10/130] Linking CXX static library /home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/build/lib/libruntimes_gtest_main.a
188.287 [1/9/131] Linking CXX shared library openmp/tools/omptest/libomptest.so
201.466 [1/8/132] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/tools.cpp.o
229.424 [1/7/133] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/reduce.cpp.o
392.625 [1/6/134] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/character.cpp.o
474.601 [1/5/135] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/dot-product.cpp.o
command timed out: 1200 seconds without output running [b'ninja'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2636.463920

```

</details>

https://github.com/llvm/llvm-project/pull/189295