[librsvg/librsvg-2.48] Fix Makefile.am for "make distcheck"

[Federico Mena Quintero <federico src gnome org>]

commit b85e41b72a8921e85b0a2a77558332d8f7919cfa
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri May 29 15:45:39 2020 -0500

    Fix Makefile.am for "make distcheck"

 Makefile.am | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/Makefile.am b/Makefile.am
index 92174b6a..70cb86f8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -121,6 +121,7 @@ LIBRSVG_C_API_SRC =                                         \
        librsvg/lib.rs                                          \
        librsvg/messages.rs                                     \
        librsvg/pixbuf_utils.rs                                 \
+       librsvg/benches/pixbuf_from_surface.rs                  \
        $(NULL)
 
 RUST_EXTRA =                                           \