[clang] [AMDGPU] Programmatically port old `.def` clang builtins to `.td` (PR #175873)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> > Since there's a script, should just convert all the other targets too
> 
 Also I wouldn't want to put that much change all in one PR. 

One target per PR




https://github.com/llvm/llvm-project/pull/175873