This is not a bug, it is a security feature of Virtual Box. Nevertheless it is annoying when you want to use your virutal system as a build system which needs symlinks in shared folders. To enable symlink creation, do the following:
Shut down your virtual machine, close all VirtualBox windows, including the main GUI window
VBoxManage setextradata MACHINE_LABEL VBoxInternal2/SharedFoldersEnableSymlinksCreate/SHARE_LABEL 1
For example, if your virtual machine is called “Debian Wheezy” (with a space), you have to escape that space with a backslash. In my case, I had to do:
VBoxManage setextradata Debian\ Wheezy VBoxInternal2/SharedFoldersEnableSymlinksCreate/Public 1
To check if your setting has been taken, run
VBoxManage getextradata MACHINE_LABEL enumerate
Restart your virtual machine and creating of symlinks should work. I found that creating hard links still doesn’t work with this method. If anyone knows a fix for hard links, please let me know!