[clang] [clang] Unique OverflowBehaviorTypes with a UniquingSet (NFC) (PR #223939)

[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` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/51043

<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)
...
557.673 [78/8/7653] Building CXX object tools/flang/lib/Lower/CMakeFiles/FortranLower.dir/OpenMP/OpenMP.cpp.o
557.694 [78/7/7654] Building CXX object tools/flang/lib/Lower/CMakeFiles/FortranLower.dir/Support/ReductionProcessor.cpp.o
557.738 [78/6/7655] Building CXX object tools/flang/lib/Lower/CMakeFiles/FortranLower.dir/SymbolMap.cpp.o
557.741 [78/5/7656] Building CXX object tools/flang/lib/Lower/CMakeFiles/FortranLower.dir/VectorSubscripts.cpp.o
557.839 [78/4/7657] Building CXX object tools/flang/lib/Lower/CMakeFiles/FortranLower.dir/Support/Utils.cpp.o
557.964 [77/4/7658] Building CXX object tools/flang/lib/Frontend/CMakeFiles/flangFrontend.dir/CompilerInvocation.cpp.o
558.201 [77/3/7659] Linking CXX static library lib/libFortranLower.a
558.434 [76/3/7660] Linking CXX static library lib/libflangFrontend.a
571.662 [75/3/7661] Linking CXX executable bin/bbc
703.235 [75/2/7662] Building CXX object tools/clang/lib/ASTMatchers/Dynamic/CMakeFiles/obj.clangDynamicASTMatchers.dir/Registry.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=1904.378117

```

</details>

https://github.com/llvm/llvm-project/pull/223939