fix(cli): get-target

[0xYYY]

Issue

To build from source on platforms without pre-built toolchain (e.g. x86_64 macOS), the Book instruct to run the cargo prove build-toolchain command.

In the build_toolchain command, the function get_target() will be called.

sp1/cli/src/commands/build_toolchain.rs

Line 121 in 8ac9e54

let target = get_target();

But it only returns the target triplet for the platforms with pre-built binaries and panic otherwise.

sp1/cli/src/lib.rs

Lines 65 to 77 in 8ac9e54

	#[allow(unreachable_code)]
	pub fn get_target() -> &'static str {
	#[cfg(all(target_arch = "x86_64", target_os = "linux"))]
	return "x86_64-unknown-linux-gnu";
	#[cfg(all(target_arch = "aarch64", target_os = "linux"))]
	return "aarch64-unknown-linux-gnu";
	#[cfg(all(target_arch = "aarch64", target_os = "macos"))]
	return "aarch64-apple-darwin";
	panic!("Unsupported architecture. Please build the toolchain from source.")
	}

Meaning that building from source on other platforms will encounter the following error.

Build completed successfully in 0:07:59
info: no toolchain installed for 'succinct'
Succesfully removed existing toolchain.
Found built toolchain directory at ./rust/build/x86_64-apple-darwin/stage2.
Succesfully linked the toolchain to rustup.
thread 'main' panicked at cli/src/lib.rs:74:5:
Unsupported architecture. Please build the toolchain from source.
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Solution

This PR uses the target_lexicon crate to get the target triplet of the host machine.

[tamirhemo]

Seems like we may want different functions: one to notify users that the platform is not supported, and one for getting the target when building from source. Any thoughts @ctian1 , @jtguibas ?

[0xYYY]

one to notify users that the platform is not supported

sp1/cli/src/lib.rs

Lines 79 to 91 in 8ac9e54

	#[allow(unreachable_code)]
	pub fn get_toolchain_download_url() -> &'static str {
	#[cfg(all(target_arch = "x86_64", target_os = "linux"))]
	return "https://pub-e4d9616fb885415597ff4c4d2b476ffb.r2.dev/rust-toolchain-x86_64-unknown-linux-gnu.tar.gz";
	#[cfg(all(target_arch = "aarch64", target_os = "linux"))]
	return "https://pub-e4d9616fb885415597ff4c4d2b476ffb.r2.dev/rust-toolchain-aarch64-unknown-linux-gnu.tar.gz";
	#[cfg(all(target_arch = "aarch64", target_os = "macos"))]
	return "https://pub-e4d9616fb885415597ff4c4d2b476ffb.r2.dev/rust-toolchain-aarch64-apple-darwin.tar.gz";
	panic!("Unsupported architecture. Please build the toolchain from source.")
	}

Can this function fit the need?

For example, in the install_toolchain command, both get_target() and get_toolchain_download_url() are called. get_target() determine the host machine's architecture, while get_toolchain_download_url() determine whether the host machine's architecture is supported.

sp1/cli/src/commands/install_toolchain.rs

Lines 57 to 61 in 81f01f9

	let target = get_target();
	let toolchain_asset_name = format!("rust-toolchain-{}.tar.gz", target);
	let toolchain_archive_path = root_dir.join(toolchain_asset_name.clone());
	let toolchain_dir = root_dir.join(target);
	let toolchain_download_url = get_toolchain_download_url();

[ctian1]

Thanks for the fix! LGTM