Compilation failure on `wasm32-unknown-emscripten`: `platform_impl` is defined multiple times and type mismatch in `into_abi`

[tomast1337]

When compiling a Rust project using cpal for wasm32-unknown-emscripten, the build fails due to multiple errors:

1. Duplicate module definition (E0428):

   error[E0428]: the name `platform_impl` is defined multiple times
   --> cpal-0.15.3/src/platform/mod.rs:640:1
   622 | mod platform_impl {
   | ----------------- previous definition of the module `platform_impl` here
   ...
   640 | mod platform_impl {
   | ^^^^^^^^^^^^^^^^^ `platform_impl` redefined here
   

   It seems like platform_impl is being defined twice, likely due to conditional compilation issues.

2. Type mismatch (E0308) in into_abi function:

   error[E0308]: mismatched types
   --> cpal-0.15.3/src/lib.rs:248:9
   247 | fn into_abi(self) -> Self::Abi {
   |                      --------- expected `Option<u32>` because of return type
   248 | match self {
   249 | Self::Default => None,
   250 | Self::Fixed(fc) => Some(fc),
   251 | }
   252 | .into_abi()
   | ___________________^ expected `Option<u32>`, found `f64`
   

   The into_abi() function appears to be returning a f64, whereas the expected type is Option<u32>.

---

Steps to Reproduce:

1. Create a Rust project with cpal = "0.15.3" in Cargo.toml.

   cargo new --bin cpal_test
   cd cpal_test
   cargo add cpal --version 0.15.3

2. Compile using:

   cargo build --release --target=wasm32-unknown-emscripten

3. Observe the errors.

[kokosha]

#960 I run into this issue, but not sure how to contribute to this repository.

[kokosha]

@mitchmindtree hello, how are you? can you provide us some instruction on what is the planned host API for default platform_impl for wasm32_unknown_emscripten?