Use 'addgroup' instead of 'groupadd' in installer

[maronz]

When testing one of the generic Linux builds (e.g. 'VirtualBox-4.0.8-71778-Linux_x86.run') on a minimal distribution that lacks the 'groupadd' command the 'vboxusers' group will not be created.

Example: TinyCoreLinux, which is based on BusyBox (download: ​http://distro.ibiblio.org/tinycorelinux/3.x/release/tinycore-current.iso, currently at version 3.6)

The issue could be easily avoided if on those systems in 'install.sh' a command like "addgroup -S $GROUPNAME" instead of "groupadd $GROUPNAME" would be executed.

After checking a few of the "big" (or should one rather say "bloated") distributions (e.g. Natty Narwhal or FC-14) I've realized that not all are having 'addgroup' in their base, so first a check of the availability of the respective command would be required.

[MSumulong]

Yes, I had the same issue installing the GA into Tiny Core. I was able to work around it by issuing the following commands before installing the GA:

sudo addgroup -g 1 -S vboxsf
sudo adduser -h /var/run/vboxadd -G vboxsf -S -s /bin/false vboxadd
sudo addgroup tc vboxsf

This seemed to add the users/groups correctly.