814b827efe
Only export `__tls_*` on wasm32-unknown-unknown. From talking with `@abrown,` we aren't planning to have hosts call these `__tls_*` functions; instead, TLS initialization will be handled transparently within libc. Consequently, these functions don't need to be exported. Leave them exported on wasm32-unknown-unknown though, as wasm-bindgen does call them.
Please read the rustc-dev-guide chapter on Backend Agnostic Codegen.