cmd/link: don't include deadcoded function symbols in shared build mode
In shared build mode, we include all symbols. This includes
function symbols that are deadcoded by the compiler. They don't
really get compiled, and their metadata may be missing, causing
linker failures. Skip them.
Fixes #67635.
Change-Id: Ic0e64bd032be499cca26da5e9e3ffbe9998bac05
Reviewed-on: https://go-review.googlesource.com/c/go/+/588316 Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>