An out-of-sync uniffi-bindgen tool can create bugs

[thunderbiscuit]

The uniffi_bindgen_generate.sh script calls the uniffi-bindgen cli tool installed on the user's local machine, but if the tool is out of sync with the rest of the uniffi libraries used in Cargo.toml the bindings produced will often not work.

The long-term solution used by Mozilla and which we adopted in the bdk-ffi repo is to create and maintain within the repo a small cli tool which we call ourselves to generate the bindings file, in effect controlling which version of uniffi_bindgen is used to generate the glue file.

The short-term solution is to just add a note to the readme that specifies which version of the uniffi-bindgen tool developers should have on the local setup before running the uniffi_bindgen_generate.sh script. At the moment this is version 0.21.0, which can be downloaded using

cargo install uniffi_bindgen --version 0.21.0

[tnull]

Done, as I now upgraded #25 to UniFFI 0.23.0, which deprecates the standalone uniffi_bindgen (and hence forced me to build it locally).