Clang float 128 bug now in GitHub llvm issue 46903 with first solution

[stefano2734]

Clang float128 bug in readme for hip sycl and cuda:

In Gitlab https://bugs.llvm.org/show_bug.cgi?id=47559

In GitHub https://github.com/llvm/llvm-project/issues/46903

With a work around to clang 19.1, but issue 46903 not closed

https://github.com/llvm/llvm-project/commit/318bff6811e7a7e0d3295ed85aa3ad01d475cc8c

Actual is clang 20.1.8 and a new test about this bug is possible.