Always go through rustup proxies

[topjohnwu]

No description provided.

[Copilot]

Pull Request Overview

This PR ensures that Rust builds always go through rustup proxies by updating dependency formatting, build configurations, and documentation.

• Reformats dependency definitions in Cargo.toml and enables binary stripping.
• Updates documentation to instruct users to install rustup and link the toolchain properly.
• Refactors build.py to route cargo invocations via rustup and adjust environment setups.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
native/src/Cargo.toml	Reformats library dependency definitions and changes the strip flag to true.
docs/build.md	Updates development instructions to use rustup and clarifies toolchain linking steps.
build.py	Alters the cargo invocation by setting RUSTUP_TOOLCHAIN and refactors clippy and paths.

Comments suppressed due to low confidence (3)

native/src/Cargo.toml:67

• Enabling binary stripping may remove essential debug symbols; please confirm this change is intended for production builds rather than development.

strip = true

build.py:237

• RUSTUP_TOOLCHAIN is being set to a file system path instead of a toolchain identifier (e.g., 'stable' or 'nightly'); please verify that rustup accepts this format to ensure the proxy functions correctly.

env["RUSTUP_TOOLCHAIN"] = str(rust_sysroot)

build.py:671

• The globals for cargo and rust_bin have been removed in favor of rust_sysroot; ensure that the cargo binary is available in the system PATH when relying solely on rustup.

rust_sysroot = ndk_path / "toolchains" / "rust"