compiler,rust: No native-static-libs for wasm after 1.84

Rust 1.84 uses the latest emsdk 3.1.68 [1], and it fixed an
issue with Emscripten dynamic linking and libc [2]. After that no
native-static-libs in the output if running:

```
rustc --target=wasm32-unknown-emscripten --crate-type staticlib --print native-static-libs - < /dev/null
```

[1] rust-lang/rust#131533
[2] rust-lang/libc#4002

mesonbuild/compilers/rust.py

@@ -161,6 +161,9 @@ def _native_static_libs(self, work_dir: str, source_name: str) -> None:
                 # no match and kernel == none (i.e. baremetal) is a valid use case.
                 # return and let native_static_libs list empty
                 return
+            if self.info.system == 'emscripten':
+                # no match and emscripten is valid after rustc 1.84
+                return
             raise EnvironmentException('Failed to find native-static-libs in Rust compiler output.')
         # Exclude some well known libraries that we don't need because they
         # are always part of C/C++ linkers. Rustc probably should not print