tests/cmake/yaml/ is creating a bogus file in the source tree

[aescolar]

Describe the bug
Running the test tests/cmake/yaml/ creates a bogus file, with the extra bonus that its name is full of special characters:
tests/cmake/yaml/cmake:\n test:\n set:\n key-int: 42\n
The exact name properly escaping it is:
tests/cmake/yaml/'cmake:'$'\n'' test:'$'\n'' set:'$'\n'' key-int: 42'$'\n'
(yes, that is the file name)

To Reproduce
Steps to reproduce the behavior:

1. mkdir build; cd build
2. cmake -GNinja -DBOARD=native_sim ../tests/cmake/yaml/
3. you can now admire your new file

Note: You can remove the file from ZEPHYR_BASE with
rm tests/cmake/yaml/'cmake:'$'\n'' test:'$'\n'' set:'$'\n'' key-int: 42'$'\n'

Expected behavior
No files created in the tree

Impact
An untracked file in the git tree, and confused developers

Logs and console output
N/A

Environment (please complete the following information):

• OS: Linux, Ubuntu 24.04
• Toolchain (e.g Zephyr SDK, ...): cmake 3.28.3
• Commit SHA or Version used: main as of now da6b607

Additional context
Test introduced in 3382e28
The file is created during test_fail_missing_filename()