Ok, perhaps there are other people out there trying ISPConfig VMWare edition and who want to upgrade later on.
The error that appears will be solved by installing "binutils" via apt-get. Then ClamAV can be compiled and everything runs as expected.
But one thing is very scary. ISPConfig seems to delete the current installation or at least renders it unusable and does a "full" install on another call of "setup". In my case all my data was lost that i have setuped before. Luckily i only have one test reseller/customer/site running but this would be a major pain if i would have done more.
For future users i would really provide a newer VMWare version of ISPConfig. I mean many people are trying things out with VMWare images and in my case, i am also running these in production.