runtime: fix final stack split in exitsyscall
runtime: fix final stack split in exitsyscall

exitsyscall should be recursively nosplit, but we don't have a way to
annotate that right now (see #21314). There's exactly one remaining
place where this is violated right now: exitsyscall -> casgstatus ->
print. The other prints in casgstatus are wrapped in systemstack
calls. This fixes the remaining print.

Updates #21431 (in theory could fix it, but that would just indicate
that we have a different G status-related crash and we've *never* seen
that failure on the dashboard.)

Change-Id: I9a5e8d942adce4a5c78cfc6b306ea5bda90dbd33
Reviewed-on: https://go-review.googlesource.com/79815
Run-TryBot: Austin Clements <7ea35d812706d9213868749011af1ed4fa2f6aa0@google.com>
Reviewed-by: Rick Hudson <838bd060584c511f21c75c69ea04b7b120d86af0@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

codestation/go,josharian/go,nawawi/go,golang/go,akutz/go,josharian/go,codestation/go,cloudflare/go,cloudflare/go,cloudflare/go,Cofyc/go,golang/go,josharian/go,akutz/go,golang/go,CAFxX/go,Cofyc/go,josharian/go,nawawi/go,Cofyc/go,cloudflare/go,Cofyc/go,golang/go,codestation/go,CAFxX/go,CAFxX/go,CAFxX/go,christopher-henderson/Go,CAFxX/go,cloudflare/go,Cofyc/go,nawawi/go,akutz/go,codestation/go,akutz/go,cloudflare/go,golang/go,akutz/go,CAFxX/go,nawawi/go,golang/go,nawawi/go,golang/go,josharian/go,CAFxX/go,josharian/go,josharian/go,codestation/go,josharian/go,nawawi/go,akutz/go,akutz/go,codestation/go,CAFxX/go,cloudflare/go,nawawi/go,Cofyc/go,cloudflare/go,codestation/go,Cofyc/go,nawawi/go,Cofyc/go,akutz/go,golang/go,codestation/go