Add requirements to build binaries locally on README.md

lib/bindings/bindings-flutter/README.md

@@ -3,7 +3,28 @@
 Binding generation & build scripts for Dart/Flutter packages of Breez Liquid SDK.
 
 ## Prerequisites
+### Required
+This guide assumes you have the following tools installed on any development machines:
+- [Flutter](https://docs.flutter.dev/get-started/install)
+- [rustup](https://rustup.rs)
 - [just](https://github.com/casey/just?tab=readme-ov-file#installation) command runner.
+  - [Melos](https://melos.invertase.dev) which will be installed as part of `just bootstrap`.
+
+### Optional
+If you would like to build your binaries (for Flutter devices) locally in addition to CI 
+(say, to test on a real device or emulator), you will additionally need the following:
+- To compile to macOS/iOS targets
+  - macOS
+- To cross-compile to Android targets
+  - [Android NDK](https://developer.android.com/ndk/downloads)
+    - Most NDK versions should work nowadays due to fixes in `cargo-ndk`
+      - Previously, NDK version 21 (`r21e`) was the only one that could be used easily
+        - You might see reference to this elsewhere, but that is largely out of date
+      - NDK version 25 (`r25b`) was working at the time of writing this documentation
+- To cross-compile to Windows/Linux targets
+  - [Zig](https://ziglang.org/learn/getting-started/#installing-zig)
+  - llvm (with `clang-cl`!)
+    - Need to run `brew install llvm` on macOS since Apple's llvm doesn't have it
 
 ## Getting Started
 Run `just bootstrap` to initialize your workspace.