I've committed a patch to update libgo to the Go 1.13beta1 release.
As is usual with these updates, the patch is too large to include
here; I've included the diffs of the various GCC-specific configury
and other files.  Bootstrapped and ran Go testsuite on
x86_64-pc-linux-gnu.  Committed to mainline.

Ian

gotools:

2019-09-06  Ian Lance Taylor  <iant@golang.org>

* Makefile.am (check-carchive-test): Just run "go test", not "go
test carchive_test.go".
* Makefile.in: Regenerate.

gcc/testsuite:

2019-09-06  Ian Lance Taylor  <iant@golang.org>

* go.test/test/fixedbugs/bug369.go: Update to match libgo update
to Go 1.13beta1.