wasm-mappings fail to build with Rust 1.96+

[maxgmr]

Rust 1.96+ no longer passes --allow-undefined to wasm-ld (rust-lang/rust#149868). Previously a bare extern "C" block on wasm32-unknown-unknown implicitly imported symbols from the env module.

Now, as upstream stated, we must explicitly add the link to env.

Steps to reproduce

$ cd wasm-mappings/source-map-mappings-wasm-api
$ rustup update nightly
$ cargo +1.95.0 build --target wasm32-unknown-unknown
$ cargo +nightly build --target wasm32-unknown-unknown

Expected result

The build should pass for both toolchains.

Actual result

The build passes for Rust 1.95.0, but fails on 1.96.0+:

error: linking with `rust-lld` failed: exit status: 1
  |
[...]
  = note: rust-lld: error: /home/maxgmr/sources/source-map/wasm-mappings/source-map-mappings-wasm-api/target/wasm32-unknown-unknown/debug/deps/source_map_mappings_wasm_api.8e20wo29qqjt46oljko96p7gc.02rjxce.rcgu.o: undefined symbol: mapping_callback