sysbuild: prep-artifacts-for-testing does not support systebuild well

[hakehuang]

Describe the bug if run with below build command line, the build binary is removed from pacakge

scripts/twister --prep-artifacts-for-testing --package-artifacts test_twister_test_only.tar.gz -p nrf5340dk_nrf5340_cpuapp  -T samples/drivers/mbox/

Please also mention any information which could help others to understand the problem you're facing:

• What target platform are you using?
• nrf5340dk_nrf5340_cpuapp
• What have you tried to diagnose or workaround this issue?
• remove --prep-artifacts-for-testing works fine
• Is this a regression? If yes, have you been able to "git bisect" it to a specific commit?
• no

To Reproduce Steps to reproduce the behavior:

scripts/twister --prep-artifacts-for-testing --package-artifacts test_twister_test_only.tar.gz -p nrf5340dk_nrf5340_cpuapp  -T samples/drivers/mbox/

Expected behavior the binary with sysbuild staff can be kept

Impact --prep-artifacts-for-testing

Environment (please complete the following information):

• OS: (e.g. Linux, MacOS, Windows)
• Toolchain (e.g Zephyr SDK, ...)
• Commit SHA or Version used: 312e000a5fd1a05fe8422300af5c4452e2a69e25

[szczys]

I can confirm that I'm seeing the same behavior. The result of this operation is an archive missing all binaries, as shown by this tree:

➜ tree -a twister-out/
twister-out/
├── nrf52840dk_nrf52840
│   └── sample.golioth.fw_update.sysbuild
│       ├── build.log
│       ├── build.ninja
│       ├── CMakeCache.txt
│       ├── CMakeFiles
│       │   └── rules.ninja
│       └── zephyr
│           └── .config
├── testplan.json
└── twister.json