libgo: zstdpkglist.go depends on libgo-packages.txt

Change-Id: I8eebc8794f772ea07981169107a85f1fefbc6243
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/287812
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/libgo/Makefile.am b/libgo/Makefile.am
index 6188725..7be90a5 100644
--- a/libgo/Makefile.am
+++ b/libgo/Makefile.am
@@ -656,7 +656,7 @@
 
 # Generate the list of go std packages that were included in libgo
 zstdpkglist.go: s-zstdpkglist; @true
-s-zstdpkglist: Makefile
+s-zstdpkglist: Makefile libgo-packages.txt
 	rm -f zstdpkglist.go.tmp
 	echo 'package goroot' > zstdpkglist.go.tmp
 	echo "" >> zstdpkglist.go.tmp
diff --git a/libgo/Makefile.in b/libgo/Makefile.in
index daae4f8..c52723b 100644
--- a/libgo/Makefile.in
+++ b/libgo/Makefile.in
@@ -2828,7 +2828,7 @@
 
 # Generate the list of go std packages that were included in libgo
 zstdpkglist.go: s-zstdpkglist; @true
-s-zstdpkglist: Makefile
+s-zstdpkglist: Makefile libgo-packages.txt
 	rm -f zstdpkglist.go.tmp
 	echo 'package goroot' > zstdpkglist.go.tmp
 	echo "" >> zstdpkglist.go.tmp