libgo: don't put golang.org packages in zstdpkglist.go

This ensures that internal/goroot.IsStandardPackage does not treat
golang.org packages as being in the standard library.

For golang/go#41368
Fixes golang/go#41499

Change-Id: I58abc84c6c8544b3d7f513bda7a5e5a63d0a9937
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/256319
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/libgo/Makefile.am b/libgo/Makefile.am
index 9ce0cab..e3f08a2 100644
--- a/libgo/Makefile.am
+++ b/libgo/Makefile.am
@@ -620,7 +620,7 @@
 	echo 'package goroot' > zstdpkglist.go.tmp
 	echo "" >> zstdpkglist.go.tmp
 	echo 'var stdpkg = map[string]bool{' >> zstdpkglist.go.tmp
-	echo $(libgo_go_objs) 'unsafe.lo' 'runtime/cgo.lo' | sed 's|[a-z0-9_./]*_c\.lo||g' | sed 's|\([a-z0-9_./]*\)\.lo|"\1": true,|g' >> zstdpkglist.go.tmp
+	echo $(libgo_go_objs) 'unsafe.lo' 'runtime/cgo.lo' | sed 's|[a-z0-9_./]*_c\.lo||g' | sed 's|golang\.org/[a-z0-9_./]*\.lo||g' | sed 's|\([a-z0-9_./]*\)\.lo|"\1": true,|g' >> zstdpkglist.go.tmp
 	echo '}' >> zstdpkglist.go.tmp
 	$(SHELL) $(srcdir)/mvifdiff.sh zstdpkglist.go.tmp zstdpkglist.go
 	$(STAMP) $@
diff --git a/libgo/Makefile.in b/libgo/Makefile.in
index b577083..18b1a06 100644
--- a/libgo/Makefile.in
+++ b/libgo/Makefile.in
@@ -2784,7 +2784,7 @@
 	echo 'package goroot' > zstdpkglist.go.tmp
 	echo "" >> zstdpkglist.go.tmp
 	echo 'var stdpkg = map[string]bool{' >> zstdpkglist.go.tmp
-	echo $(libgo_go_objs) 'unsafe.lo' 'runtime/cgo.lo' | sed 's|[a-z0-9_./]*_c\.lo||g' | sed 's|\([a-z0-9_./]*\)\.lo|"\1": true,|g' >> zstdpkglist.go.tmp
+	echo $(libgo_go_objs) 'unsafe.lo' 'runtime/cgo.lo' | sed 's|[a-z0-9_./]*_c\.lo||g' | sed 's|golang\.org/[a-z0-9_./]*\.lo||g' | sed 's|\([a-z0-9_./]*\)\.lo|"\1": true,|g' >> zstdpkglist.go.tmp
 	echo '}' >> zstdpkglist.go.tmp
 	$(SHELL) $(srcdir)/mvifdiff.sh zstdpkglist.go.tmp zstdpkglist.go
 	$(STAMP) $@