Cache Rust files in CI

[Desdaemon]

In CI, cargo install is called by the iOS and Android workflows which is a major bottleneck for CI. This PR caches the installed binaries along with files in select target directories.

[fzyzcjy]

LGTM once ci passes

[fzyzcjy]

No worries about the run codegen failure. I am fixing it in #678

[fzyzcjy]

Btw, I am considering sending a post in r/Rust and r/FlutterDev, and maybe hackernews? (never did the last before) What do you think?

Possible titles (still VERY, VERY rough draft!):

GUI.platforms += 1: Web is supported now, besides phones & desktops. Write UI with hot-reload and high-performance. [for r/Rust]

Using Rust (WASM) on Web now, besides phones & desktops, enpowering reliablility and performance [for r/FlutterDev]

[Desdaemon]

Btw, I am considering sending a post in r/Rust and r/FlutterDev, and maybe hackernews?

If it's HN, maybe they will appreciate the "Show HN" post format, but otherwise great idea!

[fzyzcjy]

If it's HN, maybe they will appreciate the "Show HN" post format, but otherwise great idea!

Good idea, I will do that :)

[fzyzcjy]

Will release new version around 18hrs later, when posts will be sent roughly then :)