Support for 'split-debuginfo' on wasm targets

[namse]

According to the documentation at Rust Compiler Codegen Options, setting split-debuginfo = "packed" should result in the generation of dwp files.

However, when building for wasm32-unknown-unknown and wasm32-wasip1, I was unable to obtain dwp files. In contrast, dwp files were successfully generated when building for x86_64-linux-unknown-gnu.

I hope that 'split-debuginfo' will be properly supported for wasm targets as well.

[bjorn3]

https://github.com/rust-lang/thorin needs to add support for reading and writing wasm files before -Csplit-debuginfo=packed can be supported. -Csplit-debuginfo=unpacked is already supported as unstable feature when -Zunstable-options is passed.