I'm working on the automation of installing Debian by using the preseed mechanism. The final install question that keeps popping up warns me about an EFI installation. It says an EFI installation may make existing operating systems on the disk unbootable. It gives me the choice to install in BIOS legacy mode.
I do not care about an already installed operating system. The new install is supposed to use the complete disk (partman preseed parameters).
How do I answer this question/warning in the preseed file such that it does not hinder an automated install?