[librsvg] Add source files for recently added benchmarks to Makefile.am

[Sven Neumann <sneumann src gnome org>]

commit f01c309f92a393555caab0d54d3bbb6600c6e375
Author: Sven Neumann <sven svenfoo org>
Date:   Sat Oct 17 16:08:32 2020 +0200

    Add source files for recently added benchmarks to Makefile.am
    
    This fixes 'make distcheck'.

 Makefile.am | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/Makefile.am b/Makefile.am
index 1d77e855..b13bffc7 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -141,7 +141,9 @@ RUST_EXTRA =                                                \
        rsvg_internals/benches/lighting.rs              \
        rsvg_internals/benches/path_parser.rs           \
        rsvg_internals/benches/pixel_iterators.rs       \
+       rsvg_internals/benches/pixel_ops.rs             \
        rsvg_internals/benches/srgb.rs                  \
+       rsvg_internals/benches/surface_from_pixbuf.rs   \
        rsvg_internals/src/ua.css                       \
        $(NULL)