As titled, adding version file to kselftest installation dir, so the user
of the tarball can know which kernel version the tarball belongs to.
Link: https://lore.kernel.org/r/20250610221248.819519-1-1997cui@gmail.com
Signed-off-by: Tianyi Cui <1997cui@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>