cmd/link: don't create __x86.get_pc_thunk symbol if it already exists
On 386, in some build modes we need to create the __x86.get_pc_thunk
symbols, to support PC-relative addressing. In some situation
the thunk symbols may already exist, e.g. loaded from a C object
in internal linking mode. In this case, we should use the exiting
symbol instead of making a new one. The current code updates the
symbol content in place but also adds a duplicated entry to Textp,
which breaks the address sorting order.
Fixes #76815.
Change-Id: Iab11106ce592dc5219b7a0e07cfafcd270661a2f
Reviewed-on: https://go-review.googlesource.com/c/go/+/730161 Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>