[release-branch.go1.12] doc: document Go 1.11.8

Change-Id: Ia06f7005f466e55a22c76bf2b47d74ee8eb77dd1
Reviewed-on: https://go-review.googlesource.com/c/go/+/171139Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit 739a78f2)
Reviewed-on: https://go-review.googlesource.com/c/go/+/171145Reviewed-by: Andrew Bonventre <andybons@golang.org>

doc/devel/release.html

@@ -121,6 +121,14 @@ go1.11.7 (released 2019/04/05) includes fixes to the runtime and the
 1.11.7 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.11.8 (released 2019/04/08) fixes an issue where using the prebuilt binary
+releases on older versions of GNU/Linux
+<a href="https://golang/go/issues/31293">led to failures</a>
+when linking programs that used cgo.
+Only Linux users who hit this issue need to update.
+</p>
+
 <h2 id="go1.10">go1.10 (released 2018/02/16)</h2>
 
 <p>