Avoid using make_direct_deprecated() in extern "ptx-kernel"
This method will be removed in the future as it produces a broken ABI that depends on cg_llvm implementation details. After this PR wasm32-unknown-unknown is the only remaining user of make_direct_deprecated().
Fixes https://github.com/rust-lang/rust/issues/117271
Blocks https://github.com/rust-lang/rust/issues/38788