[source] download.mk: improve download tarball reproducibility

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/1b9a39c528bcad4f66821e15f8c2162075a40191

commit 1b9a39c528bcad4f66821e15f8c2162075a40191
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Mon Dec 12 13:12:43 2016 +0100

    download.mk: improve download tarball reproducibility
    
    Store only numeric user/group id. Group 0 is 'root' on linux and 'wheel' on
    BSD and Mac OS X.
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 include/download.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/download.mk b/include/download.mk
index 49d2bf3..3c6b4a2 100644
--- a/include/download.mk
+++ b/include/download.mk
@@ -41,7 +41,7 @@ define dl_pack
 	$(if $(dl_pack/$(call ext,$(1))),$(dl_pack/$(call ext,$(1))),$(dl_pack/unknown))
 endef
 define dl_tar_pack
-	$(TAR) --owner=0 --group=0 --sort=name $$$${TAR_TIMESTAMP:+--mtime="$$$$TAR_TIMESTAMP"} -c $(2) | $(call dl_pack,$(1))
+	$(TAR) --numeric-owner --owner=0 --group=0 --sort=name $$$${TAR_TIMESTAMP:+--mtime="$$$$TAR_TIMESTAMP"} -c $(2) | $(call dl_pack,$(1))
 endef
 
 define DownloadMethod/unknown