tools: squashfs3-lzma: generate reproducible output

Always initialize header with zeros as otherwise we may end up with
uninitialized memory which ruins reproducibility.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

tools/squashfs3-lzma/patches/150-fix-unitialized-memory.patch

@@ -0,0 +1,11 @@
+--- a/squashfs-tools/mksquashfs.c
++++ b/squashfs-tools/mksquashfs.c
+@@ -1822,7 +1822,7 @@ int main(int argc, char *argv[])
+ {
+ 	struct stat buf, source_buf;
+ 	int i;
+-	squashfs_super_block sBlk;
++	squashfs_super_block sBlk = {};
+ 	char *b, *root_name = NULL;
+ 	int be, nopad = FALSE, keep_as_directory = FALSE, orig_be;
+ 	squashfs_inode inode;