_content/doc: mention cgo requirements for external linking in release notes for Go 1.21 and 1.22

Fixes golang/go#65887.
Updates golang/go#31544.
Updates golang/go#46330.
Updates golang/go#64875.

Change-Id: Ibb035e2287ad0efdbe875c5dd16ffd938ec7a956
Reviewed-on: https://go-review.googlesource.com/c/website/+/569296
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

_content/doc/go1.21.md

@@ -205,6 +205,11 @@ The `go` `test` `-o` flag now
 accepts a directory argument, in which case test binaries are written to that
 directory instead of the current directory.
 
+<!-- https://go.dev/issue/31544, CL 477839 -->
+When using an external (C) linker with cgo enabled, the `runtime/cgo` package is
+now supplied to the Go linker as an additional dependency to ensure that the Go
+runtime is compatible with any additional libraries added by the C linker.
+
 ### Cgo {#cgo}
 
 <!-- CL 490819 -->

_content/doc/go1.22.html

@@ -125,6 +125,14 @@ func main() {
   will continue to report that there are no test files.
 </p>
 
+<!-- CL 522239, https://go.dev/issue/46330 -->
+<p>
+  <code>go</code> build commands that invoke the linker now error out if an
+  external (C) linker will be used but cgo is not enabled. (The Go runtime
+  requires cgo support to ensure that it is compatible with any additional
+  libraries added by the C linker.)
+</p>
+
 
 <h3 id="trace">Trace</h3>