runtime: avoid staticinit dependency with sigsetAllExiting

Currently, package runtime runs `osinit` before dynamic initialization
of package-scope variables; but on GOOS=linux, `osinit` involves
mutating `sigsetAllExiting`.

This currently works because cmd/compile and gccgo have
non-spec-conforming optimizations that statically initialize
`sigsetAllExiting`, but disabling that optimization causes
`sigsetAllExiting` to be dynamically initialized instead. This in turn
causes the mutations in `osinit` to get lost.

This CL moves the initialization of `sigsetAllExiting` from `osinit`
into its initialization expression, and then removes the special case
for continuing to perform the static-initialization optimization for
package runtime.

Updates #51913.

Change-Id: I3be31454277c103372c9701d227dc774b2311dad
Reviewed-on: https://go-review.googlesource.com/c/go/+/405549
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

0 files changed, 0 insertions, 0 deletions