[librsvg] Appease autotools a bit by not using _SOURCES suffixes

[Federico Mena Quintero <federico src gnome org>]

commit 65bac77a2e4ae217a4340bceaddd82634bfbdca6
Author: Federico Mena Quintero <federico gnome org>
Date:   Mon Aug 26 16:23:05 2019 +0300

    Appease autotools a bit by not using _SOURCES suffixes
    
    When there is no build target that corresponds to a FOO_SOURCES
    variable, automake complains.  Use a _SRC suffix instead for the Rust sources.

 Makefile.am | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 28061ccd..91867189 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -13,7 +13,7 @@ librsvg_@RSVG_API_MAJOR_VERSION@_la_SOURCES = \
        $(librsvg_c_srcs)                       \
        $(NULL)
 
-LIBRSVG_INTERNALS_SOURCES =                                    \
+LIBRSVG_INTERNALS_SRC =                                        \
        Cargo.toml                                              \
        rsvg_internals/Cargo.toml                               \
        rsvg_internals/build.rs                                 \
@@ -99,7 +99,7 @@ LIBRSVG_INTERNALS_SOURCES =                                   \
        rsvg_internals/src/xml2_load.rs                         \
        $(NULL)
 
-LIBRSVG_CRATE_SOURCES =                                        \
+LIBRSVG_CRATE_SRC =                                    \
        librsvg_crate/Cargo.toml                                \
        librsvg_crate/build.rs                                  \
        librsvg_crate/examples/proportional.rs                  \
@@ -112,7 +112,7 @@ LIBRSVG_CRATE_SOURCES =                                     \
        librsvg_crate/tests/utils/compare_surfaces.rs           \
        $(NULL)
 
-LIBRSVG_C_API_SOURCES =                                                \
+LIBRSVG_C_API_SRC =                                            \
        librsvg/Cargo.toml                                      \
        librsvg/build.rs                                        \
        librsvg/c_api.rs                                        \
@@ -177,7 +177,7 @@ dist-hook:
        mkdir .cargo &&                                                         \
        cp cargo-vendor-config .cargo/config)
 
-librsvg_c_api.la: $(LIBRSVG_INTERNALS_SOURCES) $(LIBRSVG_C_API_SOURCES)
+librsvg_c_api.la: $(LIBRSVG_INTERNALS_SRC) $(LIBRSVG_C_API_SRC)
        +cd $(top_srcdir)/librsvg &&                                            \
        PKG_CONFIG_ALLOW_CROSS=1                                                \
        PKG_CONFIG='$(PKG_CONFIG)'                                              \
@@ -254,10 +254,10 @@ dist_doc_DATA =                           \
        code-of-conduct.md
 
 EXTRA_DIST =                           \
-       $(LIBRSVG_INTERNALS_SOURCES)    \
-       $(LIBRSVG_C_API_SOURCES)        \
+       $(LIBRSVG_INTERNALS_SRC)        \
+       $(LIBRSVG_C_API_SRC)            \
        $(RUST_EXTRA)                   \
-       $(LIBRSVG_CRATE_SOURCES)        \
+       $(LIBRSVG_CRATE_SRC)            \
        librsvg.doap                    \
        AUTHORS                         \
        NEWS                            \