install/55536: sysinst has no discoverable way to nuke-and-pave a GPT-partitioned disk

[thorpej%me.com@localhost]

>Number:         55536
>Category:       install
>Synopsis:       sysinst has no discoverable way to nuke-and-pave a GPT-partitioned disk
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Aug 03 20:05:00 +0000 2020
>Originator:     Jason Thorpe
>Release:        NetBSD 9.0
>Organization:
RISCy Business
>Environment:
(NetBSD 9.0 UEFI install image for amd64)
>Description:
sysinst has no discoverable way to nuke-and-pave a GPT-partitioned disk.

I have a Thinkpad x260 with Windows 10 installed on the built-in SSD.  I do not want to preserve the Windows installation, but rather want to take over the entire drive for NetBSD.  Ultimately, I want to end up with the following partitions:

- EFI system partition (mounted as /EFI once installation is done)
- / (root file system)
- swap
- /var
- /home (as the space sink)

All paths I take through sysinst preserve the existing GPT partitions, and make it difficult (if not impossible) to remove them.  There does not seem to be any option to zap it and start from scratch.

>How-To-Repeat:
See description.
>Fix:
None provided.  A work around might be to exit to the utility shell and manual destroy the GPT.  But that seems like unnecessary friction -- there should be an easy way to do this right from the sysinst UI.