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 nextest run, 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 nextest run locally
• 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]

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?

[chiragdhawan24]

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?

I have updated README and other files where test_translator.py was mentioned. Kindly review the changes and let me know if they're alright.

[kkysen]

Suggested change

	*Note*: The tests executed by `test_translator.py` can also be invoked simply by running `cargo nextest run` in the main c2rust workspace. `cargo nextest run` even ensures that the repo tests use the latest version of `c2rust-transpile` binary.
	Most tests are found in the [`tests`](../tests/) folder.
	Most tests can also be run with
	```sh
	cargo nextest run

which includes running the tests/unit tests.
The tests/unit tests can also be run manually using

./scripts/test_translator.py tests/unit

which also allows you to run with other options.

The tests/integration tests
aren't run automatically by cargo nextest run.
To run them, run

# Needs to be run from `tests/integration/` (or further inside)
# to correctly load the `pyproject.toml`.
cargo build --release
(export PATH=$PWD/target/release:$PATH && export C2RUST_DIR=$PWD && cd tests/integration && ./test.py curl json-c lua nginx zstd li
bxml2 python2 libmcs)

[chiragdhawan24]

I have changed the docs/README-developers.md as per the said changes in the latest commit.

Kindly re-review the same. Would really appreciate if this could now be merged into the master branch.