From f981365d1bd0e324881204d3e331b4e0d9c03a6a Mon Sep 17 00:00:00 2001
From: Joel Jeske <joel.jeske@robinhood.com>
Date: Wed, 30 Mar 2022 10:19:49 -0500
Subject: [PATCH] Use output dir for empty packages to be hermetic

---
 go/tools/builders/compilepkg.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/go/tools/builders/compilepkg.go b/go/tools/builders/compilepkg.go
index e6f5446466..04722a85a4 100644
--- a/go/tools/builders/compilepkg.go
+++ b/go/tools/builders/compilepkg.go
@@ -178,7 +178,12 @@ func compileArchive(
 	defer cleanup()
 
 	if len(srcs.goSrcs) == 0 {
-		emptyPath := filepath.Join(workDir, "_empty.go")
+		// We need to run the compiler to create a valid archive, even if there's
+		// nothing in it. GoPack will complain if we try to add assembly or cgo
+		// objects.
+		// _empty.go needs to be in a deterministic location (not tmpdir) in order
+		// to ensure deterministic output
+		emptyPath := filepath.Join(filepath.Dir(outPath), "_empty.go")
 		if err := ioutil.WriteFile(emptyPath, []byte("package empty\n"), 0666); err != nil {
 			return err
 		}