toolchain/58351: gcc12 update broke tsan signal errno corruption detection on amd64

[campbell+netbsd%mumble.net@localhost]

>Number:         58351
>Category:       toolchain
>Synopsis:       gcc12 update broke tsan signal errno corruption detection on amd64
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jun 18 12:40:01 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
The NetBSD Foundation: Undefined error: 0
>Environment:
NetBSD 10.99.10 (GENERIC) #0: Tue Jun 18 08:21:16 UTC 2024 root%babylon4.netbsd.org@localhost:/tmp/build/2024.06.18.07.21.31-amd64/obj/sys/arch/amd64/compile/GENERIC
>Description:
The t_tsan_signal_errno tests are failing since the gcc12 update:

Fail: regexp WARNING: ThreadSanitizer: signal handler spoils errno not in stderr

https://releng.netbsd.org/b5reports/amd64/2024/2024.06.18.07.21.31/test.html#usr.bin_cc_t_tsan_signal_errno_signal_errno
>How-To-Repeat:
cd /usr/tests/usr.bin/cc
atf-run t_tsan_signal_errno
>Fix:
Yes, please!