WASM bindists: wrong unlit path

Summary

When trying to compile .lhs files, a non-existent unlit is invoked.

Steps to reproduce

Consider e.g. happy which uses .lhs:

 $ cabal get happy && cd happy-*
 $ wasm32-wasi-cabal build
...
wasm32-wasi-ghc-9.7.20230425: could not execute: /nix/store/cm96a9gx16cl6837bvrqw07q6gdw1c96-wasm32-wasi-ghc-gmp/lib/wasm32-wasi-ghc-9.7.20230425/lib/bin/unlit
...

Maybe the issue is that the settings file contains

("unlit command", "$topdir/bin/unlit")

which is incorrect; the binary is named wasm32-wasi-unlit.

Expected behavior

It should work, just as it does with a manual -pgmL flag:

 $ wasm32-wasi-cabal build --ghc-options='-pgmL /path/to/lib/wasm32-wasi-ghc-9.7.20230425/bin/wasm32-wasi-unlit'

Environment

• GHC version used: Default from ghc-wasm-meta, commit 5a5c10c3b7e2f9f55bb2f40601cb20c9eb599bb5
• Operating System: NixOS
• System Architecture: x86_64-linux