[CHORE] better way to manage built fixtures

[ricochet]

Right now we don't have a script or anything tying the wasm bytes used in the test fixtures with their source code. These are not rebuilt when the source changes. It's a foot-gun that bit me pretty hard on #120

[Aditya1404Sal]

Can be closed as completed #217

[dman-os]

@Aditya1404Sal since the build script builds into examples/*/fixture/target while also rerun-if-changed on the same directories it's building in, this leads to cargo busting the cache every build. Same on the fixtures, I think.

[Aditya1404Sal]

@dman-os Thank you so much for pointing that out! I'll push out a patch ASAP

[Aditya1404Sal]

I've Created a PR which resolves this @dman-os #220