Use a GNU tar flag to shut up warnings about implausibly old timestamp

configure.ac

@@ -339,6 +339,18 @@ eval dynlib_suffix=$shrext_cmds
 AC_SUBST(dynlib_suffix)
 
 
+# Do we have GNU tar?
+AC_MSG_CHECKING([if you have GNU tar])
+if $tar --version 2> /dev/null | grep -q GNU; then
+    AC_MSG_RESULT(yes)
+    tarFlags="--warning=no-timestamp"
+else
+    AC_MSG_RESULT(no)
+fi
+AC_SUBST(tarFlags)
+
+
+
 AM_CONFIG_HEADER([config.h])
 AC_CONFIG_FILES([Makefile
    src/Makefile

corepkgs/config.nix.in

@@ -9,6 +9,7 @@ in {
   bzip2 = "@bzip2@";
   xz = "@xz@";
   tar = "@tar@";
+  tarFlags = "@tarFlags@";
   tr = "@tr@";
   curl = "@curl@";
   nixBinDir = fromEnv "NIX_BIN_DIR" "@bindir@";

corepkgs/unpack-channel.nix

@@ -6,7 +6,7 @@ let
     ''
       mkdir $out
       cd $out
-      ${bzip2} -d < $src | ${tar} xf -
+      ${bzip2} -d < $src | ${tar} xf - --warning=no-timestamp 
       mv * $out/$channelName
     '';
 

substitute.mk

@@ -22,6 +22,7 @@
 	 -e "s^@coreutils\@^$(coreutils)^g" \
 	 -e "s^@sed\@^$(sed)^g" \
 	 -e "s^@tar\@^$(tar)^g" \
+	 -e "s^@tarFlags\@^$(tarFlags)^g" \
 	 -e "s^@gzip\@^$(gzip)^g" \
 	 -e "s^@pv\@^$(pv)^g" \
 	 -e "s^@tr\@^$(tr)^g" \