[bug#48933] [PATCH] build: Make outputs of node-build-system reproducible.

[Lars-Dominik Braun <lars@6xq.net>]

package.json records two hashes of package.tgz, which change for each
build, resulting in non-reproducible builds.

* guix/build/node-build-system.scm (repack): Add reproducibility options
to tar command.
---
 guix/build/node-build-system.scm | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/guix/build/node-build-system.scm b/guix/build/node-build-system.scm
index a55cab237c..9b3de43e24 100644
--- a/guix/build/node-build-system.scm
+++ b/guix/build/node-build-system.scm
@@ -120,7 +120,15 @@
   #t)
 
 (define* (repack #:key inputs #:allow-other-keys)
-  (invoke "tar" "-czf" "../package.tgz" ".")
+  (invoke "tar"
+          ;; Add options suggested by https://reproducible-builds.org/docs/archives/
+          "--sort=name"
+          (string-append "--mtime=" (getenv "SOURCE_DATE_EPOCH"))
+          "--owner=0"
+          "--group=0"
+          "--numeric-owner"
+          "--pax-option=exthdr.name=%d/PaxHeaders/%f,delete=atime,delete=ctime"
+          "-czf" "../package.tgz" ".")
   #t)
 
 (define* (install #:key outputs inputs #:allow-other-keys)
-- 
2.31.1