posix: add posix directory and semaphore tests

[oI0ck]

JIRA: RTOS-1088

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

• Tested by hand on: ia32-generic-qemu

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).

• posixsrv: implement named semaphore server phoenix-rtos-posixsrv#27
• posix: implement POSIX semaphore interfaces libphoenix#457

• I will merge this PR by myself when appropriate.

[gemini-code-assist]

Summary of Changes

Hello @oI0ck, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new set of unit tests for POSIX named semaphores, enhancing the robustness and compliance of the system's POSIX implementation. It establishes a dedicated framework for POSIX unit tests and includes comprehensive test cases to validate various semaphore operations and behaviors.

Highlights

• Integration of POSIX unit tests: The build system (Makefile.host) has been updated to include a new category of tests, POSIX_UNIT_TESTS, ensuring they are part of the default build process.
• New POSIX test infrastructure: A dedicated 'posix/Makefile' and 'posix/test.yaml' have been introduced to manage and define POSIX-specific unit tests, providing a structured approach for future POSIX test additions.
• Comprehensive semaphore testing: A new test suite ('posix/sem/main.c' and 'posix/sem/named.c') has been added to thoroughly validate POSIX named semaphore functionalities, including 'sem_wait', 'sem_trywait', 'sem_timedwait', semaphore fairness, handling of nonexistent semaphores, and semaphore reopening.

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[gemini-code-assist]

Code Review

This pull request introduces a suite of POSIX semaphore tests. The structure and test cases are a good starting point. However, I've identified several issues within the test implementations in posix/sem/named.c. These include a missing header, incorrect usage of sem_timedwait which could lead to test failures, a race condition in the fairness test making it unreliable, and incorrect checking of errno on successful function calls. Addressing these points will improve the correctness and robustness of the new tests.