[release-branch.go1.16] cmd/link: generate trampoline for inter-dependent packages

Currently, in the trampoline generation pass we expect packages
are laid out in dependency order, so a cross-package jump always
has a known target address so we can check if a trampoline is
needed. With linknames, there can be cycles in the package
dependency graph, making this algorithm no longer work. For them,
as the target address is unkown we conservatively generate a
trampoline. This may generate unnecessary trampolines (if the
packages turn out laid together), but package cycles are extremely
rare so this is fine.

Updates #44639.
Fixes #44640.

Change-Id: I2dc2998edacbda27d726fc79452313a21d07787a
Reviewed-on: https://go-review.googlesource.com/c/go/+/292490


Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
(cherry picked from commit 098504c7)
Reviewed-on: https://go-review.googlesource.com/c/go/+/296909
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>