[clang] [clang][CUDA] Perform lvalue-to-rvalue conversion on `__cluster_dims__` attribute (PR #227998)

[Timm Baeder via cfe-commits]

tbaederr wrote:

This breaks in 

1) `Sema::ActOnGCCAsmStmtString` because we pass the APValue from `evaluateAsString()` and a `string_view` lvalue
2) in `Sema::BuiltinAssumeAligned` when the parameter is a lvalue



Point 2) is probably another missing ltor conversion, but I'm not quite sure what to do about 1).

https://github.com/llvm/llvm-project/pull/227998