[flang] [llvm] [flang][OpenMP] Change clause modifier representation in parser (PR #116656)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-sve-vls` running on `linaro-g3-03` while building `flang,llvm` at step 6 "build stage 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/143/builds/3564

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

```
Step 6 (build stage 1) failure: 'ninja' (failure)
...
[7873/8757] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/Indexing.cpp.o
[7874/8757] Building CXX object tools/clang/tools/extra/clangd/refactor/tweaks/CMakeFiles/obj.clangDaemonTweaks.dir/ExtractFunction.cpp.o
[7875/8757] Building CXX object tools/clang/tools/extra/clangd/CMakeFiles/obj.clangDaemon.dir/DumpAST.cpp.o
[7876/8757] Building CXX object tools/clang/tools/extra/clangd/CMakeFiles/obj.clangDaemon.dir/Selection.cpp.o
[7877/8757] Building CXX object tools/clang/tools/extra/clangd/CMakeFiles/obj.clangDaemon.dir/FindTarget.cpp.o
[7878/8757] Building CXX object tools/clang/tools/extra/clangd/CMakeFiles/obj.clangDaemon.dir/InlayHints.cpp.o
[7879/8757] Building CXX object tools/clang/tools/extra/clangd/CMakeFiles/obj.clangDaemon.dir/SemanticHighlighting.cpp.o
[7880/8757] Building CXX object tools/clang/tools/extra/clangd/CMakeFiles/obj.clangDaemon.dir/Diagnostics.cpp.o
[7881/8757] Building CXX object tools/clang/tools/extra/clangd/CMakeFiles/obj.clangDaemon.dir/XRefs.cpp.o
[7882/8757] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXExtractAPI.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=1530.164493

```

</details>

https://github.com/llvm/llvm-project/pull/116656