lib/60840: userland: use -ftrivial-auto-var-init

["campbell+netbsd%mumble.net@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60840
>Category:       lib
>Synopsis:       userland: use -ftrivial-auto-var-init
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Oct 02 18:45:00 +0000 2026
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
Stacme Trash Pandas LLC
>Environment:
>Description:

	As proposed on tech-userlevel:

	> I propose to enable -ftrivial-auto-var-init for all libraries
	> and utilities in userland by default (under gcc and clang),
	> and specifically to zero-initialize local variables in
	> release builds and to nonzero-initialize them in current
	> builds.

	https://mail-index.netbsd.org/tech-kern/2026/07/20/msg031158.html

	This issue is to track enabling it in all libraries and
	binaries that NetBSD ships -- but not enabling it in the
	toolchain by default for user programs, or in pkgsrc; we can
	consider those separately.

>How-To-Repeat:

>Fix: