tar: override symlink permissions

On Linux, symlink permissions cannot be altered and are always 0777.
On Mac OS X they can be 0755. Force 0777 here to keep tarballs
reproducible across systems

Signed-off-by: Felix Fietkau <nbd@nbd.name>
(cherry picked from commit e25cedd0b5)

tools/tar/patches/110-symlink-force-permissions.patch

@@ -0,0 +1,10 @@
+--- a/src/create.c
++++ b/src/create.c
+@@ -1851,6 +1851,7 @@ dump_file0 (struct tar_stat_info *st, ch
+ #ifdef HAVE_READLINK
+   else if (S_ISLNK (st->stat.st_mode))
+     {
++      st->stat.st_mode |= 0777; /* make permissions portable */
+       st->link_name = areadlinkat_with_size (parentfd, name, st->stat.st_size);
+       if (!st->link_name)
+ 	{