Seemingly breaks wasm build with rustc v1.81 unless sapp-jsutils is > v0.1.5

[caspark]

This is a super weird bug report because I don't fully understand it myself, but I have spent a few hours debugging it so I figured I'd at least share what I have in the hopes of saving someone else a few hours.

The short version is in the title: somehow, rustc 1.81 breaks my wasm build unless I upgrade sapp-jsutils to 0.1.7 (0.1.6 is MIA on crates.io), whereas with rustc 1.80 everything works just fine. Presumably there's some kind of undefined behavior going on that was totally fine until now.

Repro:

1. rustup toolchain add 1.81.0 --target wasm32-unknown-unknown
2. clone https://github.com/caspark/quad-url-breakage/ (a minimal repro w/ 2 lines of code in main())
3. install watch-exec, just and python3 if you don't have them installed yet
4. edit the justfile to either not rebuild the js file or update the paths to suit your checkouts (the js doesn't seem to be related to the problem)
5. run just web (or rm -r dist/ target/ && just web if paranoid) to make a wasm build and serve it on a localhost webserver
6. open the provided link

Observed: "unreachable code hit" error message from wasm code if you have the devtools inspector open (basically a crash/panic of some kind)

Expected: the given url is opened and the Main() ended, woo string is printed to the console.

Workaround: bumping sapp_jsutils to 0.1.7 seems to make the problem go away, though I don't know why.

Notes:

• I'm compiling on Fedora Linux for wasm32-unknown-unknown, and get the issue with both the default ld and lld.
• Naturally everything works fine for a desktop build.
• Debugging the wasm doesn't really get me anywhere since there's no source maps; instead I spent a couple hours painfully making the minimal example above via trial and error (binary search of commenting out bits of my way larger project).
• I also tried patching and reducing quad_url to the minimal thing that causes an error, and inexplicably it seems to be that removing the use sapp_jsutils::{JsObject, JsObjectWeak}; line fixes the error (if I keep that line but have nothing actually making use of those types, then everything works - but if the types are used, the error appears). This makes no sense to me, which probably indicates some gap in my understanding of the compilation/linking process.
• I haven't tried bisecting sapp_jsutils to figure out which commit between 0.1.5 and 0.1.7 actually fixes the problem (nor bisecting rustc) - that might give a bit of insight into what's going on, but I've already spent over half a day on this rabbit hole.

Anyway, I don't really expect you to root cause and fix this directly, especially because it hardly seems possible for the actual problem to be in quad_url itself, but it might be worth bumping the sapp-jsutils version just to stop others from having their time wasted. (Though I am curious if anyone else can repro the issue, and would love to actually learn what the root cause is)