[clang] [clang][SPIRV] Add builtin for OpGenericCastToPtrExplicit and its SPIR-V friendly binding (PR #137805)

[Victor Lomuller via cfe-commits]

Naghasan wrote:

Just opened a PR for this https://github.com/llvm/llvm-project/pull/141954

https://github.com/llvm/llvm-project/pull/137805