Unit_testing: Skiping all tests.

[gbarkadiusz]

Describe the bug
Twister skips all tests while running on unit_testing platform.

To Reproduce
twister -p unit_testing -T tests/ -v

Expected behavior
The tests should run on that platform.

Impact
It affects the coverage upstream.

Logs and console output

INFO    - Using Ninja..
INFO    - Zephyr version: v4.0.0-3149-gddd795a028b1
INFO    - Using 'zephyr' toolchain.
INFO    - Building initial testsuite list...
INFO    - Writing JSON report <path_to>/zephyrproject/zephyr/twister-out/testplan.json
INFO    - JOBS: 6
INFO    - Adding tasks to the queue...
INFO    - Added initial list of jobs to queue

INFO    - 2504 test scenarios (212 configurations) selected, 212 configurations filtered (212 by static filter, 0 at runtime).
Summary
├── Total test suites: 212
├── Processed test suites: 212
│   ├── Filtered test suites: 212
│   │   ├── Filtered test suites (static): 212
│   │   └── Filtered test suites (at runtime): 0
│   └── Selected test suites: 0
│       ├── Skipped test suites: 0
│       ├── Passed test suites: 0
│       ├── Built only test suites: 0
│       ├── Failed test suites: 0
│       └── Errors in test suites: 0
└── Total test cases: 3587
    ├── Filtered test cases: 3587
    └── Selected test cases: 0
        ├── Passed test cases: 0
        ├── Skipped test cases: 0
        ├── Built only test cases: 0
        ├── Blocked test cases: 0
        ├── Failed test cases: 0
        └── Errors in test cases: 0
INFO    - 0 of 0 executed test configurations passed (0.00%), 0 built (not run), 0 failed, 0 errored, with no warnings in 5.36 seconds.
INFO    - 0 of 0 executed test cases passed (0.00%) on 0 out of total 904 platforms (0.00%).
INFO    - 0 test configurations executed on platforms, 0 test configurations were only built.
INFO    - Saving reports...
INFO    - Writing JSON report <path_to>/zephyrproject/zephyr/twister-out/twister.json
INFO    - Writing xunit report <path_to>/zephyrproject/zephyr/twister-out/twister.xml...
INFO    - Writing xunit report <path_to>/zephyrproject/zephyr/twister-out/twister_report.xml...
INFO    - Run completed

Environment:

• OS: Linux
• Toolchain Zephyr SDK
• Commit SHA or Version used: Latest v4.0.0-3149-gddd795a028b

Additional context

11e656bb6a38614b663383a40e044c4941d0c841 is the first bad commit
commit 11e656bb6a38614b663383a40e044c4941d0c841
Author: Anas Nashif <anas.nashif@intel.com>
Date:   Thu Dec 5 10:16:03 2024 -0500

    twister: support testing multiple toolchain variants
    
    Added integration_toolchains to allow building/testing with multiple
    toolchains available in the environment.
    
    This changes the output structure and adds another level in the path
    under twister_out signifying the toolchain used. The toolchain used
    (variant) is also part of the json output now.
    
    Signed-off-by: Anas Nashif <anas.nashif@intel.com>

[gbarkadiusz]

@nashif FYI.