ninja: Entering directory `out/gn'
[1/1] Regenerating ninja files
[1/2668] ACTION //libcxx/include:write_config_site(//llvm/utils/gn/build/toolchain:unix)
FAILED: include/c++/v1/__config_site 
python3 ../../llvm/utils/gn/build/write_cmake_config.py -o include/c++/v1/__config_site ../../libcxx/include/__config_site.in _LIBCPP_ABI_FORCE_ITANIUM= _LIBCPP_ABI_FORCE_MICROSOFT= _LIBCPP_EXTRA_SITE_DEFINES= _LIBCPP_HAS_NO_FILESYSTEM= _LIBCPP_HAS_NO_THREADS= _LIBCPP_HAS_NO_MONOTONIC_CLOCK= _LIBCPP_HAS_MUSL_LIBC= _LIBCPP_HAS_THREAD_API_PTHREAD= _LIBCPP_HAS_THREAD_API_EXTERNAL= _LIBCPP_HAS_THREAD_API_WIN32= _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS= _LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS=1 _LIBCPP_NO_VCRUNTIME= _LIBCPP_TYPEINFO_COMPARISON_IMPLEMENTATION= _LIBCPP_HAS_NO_RANDOM_DEVICE= _LIBCPP_HAS_NO_LOCALIZATION= _LIBCPP_HAS_NO_WIDE_CHARACTERS= _LIBCPP_HAS_NO_STD_MODULES= _LIBCPP_INSTRUMENTED_WITH_ASAN= _LIBCPP_ABI_DEFINES= _LIBCPP_HARDENING_MODE_DEFAULT=_LIBCPP_HARDENING_MODE_NONE _LIBCPP_PSTL_CPU_BACKEND_LIBDISPATCH= _LIBCPP_PSTL_CPU_BACKEND_SERIAL=1 _LIBCPP_PSTL_CPU_BACKEND_THREAD= _LIBCPP_ABI_VERSION= _LIBCPP_ABI_NAMESPACE=__1 _LIBCPP_HAS_NO_TIME_ZONE_DATABASE=
Traceback (most recent call last):
  File "/usr/local/google/home/thakis/src/llvm-project/out/gn/../../llvm/utils/gn/build/write_cmake_config.py", line 122, in <module>
    sys.exit(main())
             ^^^^^^
  File "/usr/local/google/home/thakis/src/llvm-project/out/gn/../../llvm/utils/gn/build/write_cmake_config.py", line 90, in main
    if not values[var]:
           ~~~~~~^^^^^
KeyError: '_LIBCPP_PSTL_BACKEND_SERIAL'
[2/2668] AR lib/libLLVMCodeGen.a
[3/2668] LINK obj/clang/unittests/InstallAPI/InstallAPITests
[4/2668] LINK ./bin/llvm-tblgen
[5/2668] LINK obj/llvm/unittests/FuzzMutate/FuzzMutateTests
[6/2668] LINK ./bin/llvm-link
[7/2668] LINK obj/llvm/unittests/Transforms/IPO/IPOTests
ninja: build stopped: subcommand failed.
Command '['ninja', '-C', 'out/gn']' returned non-zero exit status 1.