Default project starting point generates unexpectedly large .wasm file

[MichaelMBradley]

🐛 Bug description

When building the default provided project in release mode without the console panic hook, the size of the output .wasm file is 13KB, more than I would expect for such logic and much more than the 172 byte add example.

🤔 Expected Behavior

Much smaller wasm file is generated.

👟 Steps to reproduce

Create a new project with wasm-pack new wasm.
Comment out the console_error_panic_hook feature in Cargo.toml (after which the compiler correctly points out that set_panic_hook() is never used).
Build with wasm-pack build --release.
Check code size with ls -l pkg/wasm_bg.wasm (13294 bytes).
Note: Enabling LTO and setting opt-level = "z" in Cargo.toml didn't alter the size of the generated code, and stdout indicates that wasm-opt was found and used for optimization.

Alternatively:
Replace code in src/lib.rs with the basic add example.
Compile as above, check code size (13226 bytes).

🌍 Your environment

Include the relevant details of your environment.
wasm-pack version: 0.13.0
rustc version: 1.80.0

Arch Linux 6.10.3, wasm-bindgen installed through Cargo, wasm-opt installed through system binaryen package.

I first noticed this when analyzing the code size of some basic functions I'd implemented in another project and found there was 13KB I just couldn't drop, even trying to avoid allocating memory, possible panics and string formatting. When compiling with --dev and passing the output to twiggy I see plenty of space taken up by these sorts of functions, but that hasn't been passed through wasm-opt so that may not mean anything (when I do optimize it the names provided by twiggy are meaningless to me e.g. code[0] at 4650 bytes, data[3] at 1982 bytes, etc.).

I've also included the output from cargo rustc --release -- --emit llvm-ir: llvm-ir.txt