[llvm-branch-commits] [libcxx] Workaround for build error after #108999 (PR #110783)

[Vitaly Buka via llvm-branch-commits]

https://github.com/vitalybuka created https://github.com/llvm/llvm-project/pull/110783

```
FAILED: include/c++/v1/libcxx.imp ./libcxx_build_msan/include/c++/v1/libcxx.imp
cd ./libcxx_build_msan/libcxx/include && /usr/bin/python3 ./llvm-project/libcxx/utils/generate_iwyu_mapping.py -o ./libcxx_build_msan/include/c++/v1/libcxx.imp
Traceback (most recent call last):
  File "./llvm-project/libcxx/utils/generate_iwyu_mapping.py", line 94, in <module>
    main(sys.argv[1:])
  File "./llvm-project/libcxx/utils/generate_iwyu_mapping.py", line 84, in main
    raise RuntimeError(f"{header}: Header {public} is not a valid header")
RuntimeError: __cxx03/__algorithm/all_of.h: Header cxx03 is not a valid header
ninja: build stopped: subcommand failed.

```