Force usage of gtar

Index: scripts/miscellaneous/tar.m
--- scripts/miscellaneous/tar.m.orig
+++ scripts/miscellaneous/tar.m
@@ -70,7 +70,7 @@ function filelist = tar (tarfile, files, rootdir = "."
     cmd = sprintf ("tar cvf %s -C %s %s 2>&1",
                             tarfile, rootdir, sprintf (" '%s'", files{:}));
   else
-    cmd = sprintf ("tar cvf %s -C %s %s",
+    cmd = sprintf ("gtar cvf %s -C %s %s",
                             tarfile, rootdir, sprintf (" %s", files{:}));
   endif