[clang] Reland [CUDA][HIP] Fix CTAD for host/device constructors (#168711) (PR #170481)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

> > > Hey @yxsamliu - I am not sure that design makes sense in the long term. If there is really a concern that your previous PR is disruptive (do you have more data?)
> > > Can we
> > > 
> > > * Add documentation stating adding target attributes on deduction guides will not be supported in a future version of Clang
> > > * Add a depreciation warning.
> > > 
> > > Would that be an acceptable direction for ROCm?
> > > Thanks!
> > 
> > 
> > So far I only see rocRand using host+device attributes on deduction guide.
> > I will see whether a deprecation warning causes any CI failures.
> 
> updated the PR to include a deprecation warning for host+device attrs on deduction guide.
> 
> will open an issue for rocRand to remove the host+device attrs on deduction guide.

BTW, internal CI passes with the deprecation warning.

https://github.com/llvm/llvm-project/pull/170481