libostree: Allow compression level to be set for archive-z2 stream

Add a ostree_raw_file_to_archive_z2_stream_with_options() variant of
ostree_raw_file_to_archive_z2_stream(), to allow a compression-level
option to be passed in and passed through to zlib.

This is useful when building archive-z2 files on the fly for
transmission over a non-bandwidth-limited channel, such as a local
network. In this case, CPU time is more valuable than bandwidth, so we
want a low compression level.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Closes: #721
Approved by: cgwalters

src/libostree/ostree-core.h

@@ -311,6 +311,16 @@ ostree_raw_file_to_archive_z2_stream (GInputStream       *input,
                                       GCancellable       *cancellable,
                                       GError            **error);
 
+_OSTREE_PUBLIC
+gboolean
+ostree_raw_file_to_archive_z2_stream_with_options (GInputStream       *input,
+                                                   GFileInfo          *file_info,
+                                                   GVariant           *xattrs,
+                                                   GVariant           *options,
+                                                   GInputStream      **out_input,
+                                                   GCancellable       *cancellable,
+                                                   GError            **error);
+
 _OSTREE_PUBLIC
 gboolean ostree_raw_file_to_content_stream (GInputStream       *input,
                                             GFileInfo          *file_info,