Summary:
This is going to be deprecated in
https://github.com/llvm/llvm-project/pull/112849. This patch ports it to
use the builtin instead. This isn't a compile constant, so it could
slightly negatively affect codegen. There really should be an IR pass to
turn it into a constant if the function has known attributes.

Using the builtin is correct when we just do it for knowing the size
like we do here. Obviously guarding w32/w64 code with this check would
be broken.

Many tests in the `offload` project have requirements defined by which
targets are not supported rather than which platforms are supported.
This patch aims to streamline the requirement definitions by adding four
new feature tags: `host`, `gpu`, `amdgpu`, and `nvidiagpu`.

Summary:
We don't have the abs function to link against, just use the builtin.

This reverts commit 7b4865582299294455bc816358fd88a9c6e5e0be.

This reverts commit 9b31cc71d66064dfaf2afabf4a835211321bb4a0.

This reverts commit 098c6dfa8157681699a71fce9e3d94515e66311f.
This reverts commit 8c718a3a91df4ab68dc3f1ca3887ea730c9aed84.
This reverts commit 4fb02de9d490d0773441aa30124bb4d1272230d3.