Adds the `#llvm.target<triple = $TRIPLE, chip = $CHIP, features =
$FEATURES>` attribute and along with a `-llvm-target-to-data-layout`
pass to derive a MLIR data layout from the LLVM data layout string
(using the existing `DataLayoutImporter`). The attribute implements the
relevant DLTI-interfaces, to expose the `triple`, `chip` (AKA `cpu`) and
`features` on `#llvm.target` and the full `DataLayoutSpecInterface`. The
pass combines the generated `#dlti.dl_spec` with an existing `dl_spec`
in case one is already present, e.g. a `dl_spec` which is there to
specify size of the `index` type.
Adds a `TargetAttrInterface` which can be implemented by all attributes
representing LLVM targets.
Similar to the Draft PR https://github.com/llvm/llvm-project/pull/78073.
RFC on which this PR is based:
https://discourse.llvm.org/t/mandatory-data-layout-in-the-llvm-dialect/85875
cbfa265e98