OSX rust setup items to check if you are having trouble building the default project

[bobwith2bees]

Just capturing two gotcha's I encountered. Coming from the Flutter/Dart camp, I had only played with Rust a few times before on my OSX Box. Of course that's what got me into trouble, so passing on my lessons learned.

1. Uninstall any brew managed rust and rustup. (brew uninstall rust rustup) Then follow directions here https://www.rust-lang.org/tools/install .

Why? - I was having errors that the crates for stdlib were missing. rustup target add didn't seem to install them with my brew managed setup. I hit some articles that had strong opinions that cross compile project like flutter_rust_bridge should avoid brew managed rust. Could also be related to #2...

2. Verify your rustup show active-toolchain matches your hardware platform uname -m. OSX on an arm64 can run the x86 version of the build tools. I corrected this with rustup default stable-aarch64-apple-darwin on my M2 (arm64) machine.

Why? - I found the script rust_builder/cargokit/run_build_tool.sh would error out when I had a mismatch when creating the build tools on the fly. It was confusing since I was building for mobile and I was getting an error related to darwin. It took me a while to notice the x86 toolchain was active, and then I realized what might be the problem.

Hope this helps.

[fzyzcjy]

Looks great and thanks for sharing!