cmd/go/internal/load: clone pgo variant's PackagePublic.Imports in split
Before this change the pgo and non-pgo variants Imports slices pointed
to the same array, so modifying the pgo variant's Imports slice to add
the .ForMain suffix modified the non-pgo vairant's Imports slice too.
This change clones the imports slice to avoid that.
Fixes #66218
Change-Id: Ic936086f2c31f2056988d6546216142e4fce4d8d
Reviewed-on: https://go-review.googlesource.com/c/go/+/588275 Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Auto-Submit: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Than McIntosh <thanm@google.com>