install_packages: check for debian

[Thomas Lange]

Hi Maximilian,

thanks for the hint. I've already applied a patch which will be
available in the next upcoming FAI version (6.2.1).

regards Thomas

>>>>> On Tue, 20 Feb 2024 17:31:25 +0100, Maximilian Stein <m at steiny.biz> said:

    > Hi there,
    > to decide if it is running on a Debian system, install_packages(8) 
    > switched to checking for existence of 
    > $FAI_ROOT/var/cache/apt/pkgcache.bin a while ago [1].

    > Unfortunately, this does not always work in my tests with Bookworm, as 
    > the file seems to be deleted and recreated during an apt update.