transpile: tests: Run test_translator.py from cargo nextest with the currently built transpiler path

[chiragdhawan24]

• Fixes Issue Automatically compile c2rust before running tests #1398

When running the tests, test_translator.py could end up using a stale c2rust/c2rust-transpile binary unless cargo build --release had been run manually beforehand.

This change updates the test flow so repo tests use the latest version of c2rust-transpile binary built by cargo test, by passing the current transpiler path into test_translator.py and overriding the configured transpiler path for that test run.

This removes the manual pre-build requirement and makes local test execution less error-prone.

Testing:

• ran cargo test -- --nocapture
• verified that test_translator.py was invoked, and it received the expected c2rust-transpile path
• confirmed the tests ran successfully without manually running cargo build --release

[kkysen]

Suggested change

	"test_translator.py failed with status: {}",
	status
	"test_translator.py failed with status: {status}"

[kkysen]

Could you also print the whole command that failed? Like this

let mut cmd = Command::new("../scripts/test_translator.py");
cmd.args(["../tests/unit", "--transpiler"]);
cmd.arg(transpile_path);
let status = cmd.status().unwrap_or_else(|e| panic!("{cmd:?} failed: {e}");
assert!(status.success(), "{cmd:?} failed with {status}");

[chiragdhawan24]

I have addressed this in the latest commit.

[kkysen]

Thanks for this! A few other things:

We use cargo nextest run instead of cargo test, so run that locally instead.

Can you update the README and anywhere else that references test_translator.py to say you can also just run cargo nextest run?