llvm 14 update: libcxxabi build error

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

I've started updating the llvm packages to 14.0.6 and got llvm and
clang to build, but in libcxxabi/libcxx I see a build failure on
9.99.98/amd64:

In file included from /scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/__compare/strong_order.h:12,
                 from /scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/__compare/weak_order.h:14,
                 from /scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/__compare/partial_order.h:14,
                 from /scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/__compare/compare_partial_order_fallback.h:13,
                 from /scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/compare:144,
                 from /scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/utility:236,
                 from /scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/__functional_base:26,
                 from /scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/memory:808,
                 from /scratch/lang/libcxxabi/work/libcxxabi-14.0.6.src/../libcxx/src/include/atomic_support.h:13,
                 from /scratch/lang/libcxxabi/work/libcxxabi-14.0.6.src/src/cxa_default_handlers.cpp:19:
/scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/__bit/bit_cast.h: In function 'constexpr _ToType std::__1::bit_cast(const _FromType&)':
/scratch/lang/libcxxabi/work/libcxx-14.0.6.src/include/__bit/bit_cast.h:31:38: error: expected primary-expression before ',' token
   31 |     return __builtin_bit_cast(_ToType, __from);
      |                                      ^

I found https://github.com/llvm/llvm-project/issues/54018 which also
contains this error message, but I don't know how to work around this.

I've pushed what I have to wip/, all help welcome!
 Thomas