test: clean up linker tests

[ghaith]

This PR applies some small cosmetic fixes and addresses a review comment for the recent linker changes.
The linker changes were accidentally commited in another PR before they were approved.

[Copilot]

Pull request overview

Improves RuSTy’s linker invocation and configuration to support linking by exact library filenames or full paths, and adds new CLI switches for controlling linker/driver behavior while updating docs and tests accordingly.

Changes:

• Added libraries.link_path support in plc.json and documented/link-tested linking via exact filenames and full paths.
• Introduced new linker-related CLI flags (--fuse-ld, --linker-arg, --nocrt, --nolibc) and propagated them through the driver pipeline.
• Refactored internal/external linker resolution and expanded test coverage + documentation.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/integration/linking.rs	Adjusts integration tests to use --nocrt with updated linker behavior.
tests/integration/external_files.rs	Adds --nocrt to static compilation integration test path.
tests/integration/data/json/build_with_link_path.json	New build-config fixture demonstrating libraries.link_path.
tests/integration/command_line_compile.rs	Adds --nocrt to a CLI integration test invocation.
tests/integration/build_description_tests.rs	Adds integration test that exercises link_path through plc build.
src/linker.rs	Major linker resolution refactor; adds driver-mode features and full-path -l handling.
compiler/plc_project/src/project.rs	Resolves link_path to an actual file and uses it for link name.
compiler/plc_project/src/build_config.rs	Adds link_path to LibraryConfig and parsing test.
compiler/plc_project/schema/plc-json.schema	Extends JSON schema with link_path.
compiler/plc_driver/src/pipelines.rs	Wires new linker options (fuse_linker, args, nocrt, nolibc) into link step.
compiler/plc_driver/src/main.rs	Initializes logging based on parsed CLI log-level flags.
compiler/plc_driver/src/lib.rs	Extends LinkOptions with new linker-control fields.
compiler/plc_driver/src/cli.rs	Adds log-level flags and new linker-control flags + CLI tests.
book/src/using_rusty/build_configuration.md	Documents libraries.link_path and additional linker options for build.
book/src/using_rusty.md	Documents new CLI linker flags and enriched -l behavior.
book/src/libraries.md	Documents exact-filename and full-path -l forms; updates build-config terminology.

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