Modify release asset preparation in workflow

[tomassrnka]

Updated the workflow to prepare release assets by copying vmlinux binaries to a new directory before uploading.

---

Note

Collects vmlinux binaries into release-assets and uploads those files instead of the raw builds directory.

• CI workflow (.github/workflows/fc-kernels.yml):
  • Add step to assemble release assets: copy each vmlinux.bin from ./builds/*/ into release-assets/ as vmlinux-<variant>.bin.
  • Update release upload to target ./release-assets/* instead of ./builds/**.

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[jakubno]

Do you know why it worked before and now it doesn't and how does this fixes the issue?

[tomassrnka]

Has there ever been 2 kernel versions in parallel? Cause the current code fails as both builds have "vmlinux" as a result..