Rust: Preinstall extractor toolchain in tests

Install Rust 1.97.0 before parallel integration and QL tests start, avoiding concurrent rustup auto-installation races.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 28cef7d1-ef57-48e7-aba0-e63e74f97d92

Author: paldepind

rust/ql/integration-tests/conftest.py

@@ -5,6 +5,14 @@
 import tomllib
 
 
+def pytest_configure(config):
+    # Install before xdist starts its workers to avoid concurrent rustup downloads.
+    if not hasattr(config, "workerinput"):
+        commands.run(
+            "rustup toolchain install 1.97.0 --profile minimal --component rust-src"
+        )
+
+
 @pytest.fixture(params=[2018, 2021, 2024])
 def rust_edition(request):
     return request.param

rust/ql/test/setup.sh

@@ -8,6 +8,8 @@ set -euo pipefail
 
 # no need to install rust-src explicitly, it's listed in both toolchains
 cd "$(dirname "$0")"
+# toolchain forced by the extractor for rust-analyzer compatibility
+rustup toolchain install 1.97.0 --profile minimal --component rust-src
 pushd ../../extractor/src/nightly-toolchain
 rustup install
 popd