gnu: Use librsvg-bootstrap.

* gnu/packages/emacs.scm (emacs)[inputs]: Use librsvg-bootstrap.
* gnu/pacakges/gtk.scm (gtk+-2, gtk+)[propagated-inputs]: Same.

gnu/packages/emacs.scm

@@ -288,7 +288,9 @@
        ;; must also provide zlib as an input.
        ("libpng" ,libpng)
        ("zlib" ,zlib)
-       ("librsvg" ,(librsvg-for-system))
+       ("librsvg" ,@(if (target-x86-64?)
+                         (list librsvg-bootstrap)
+                         (list librsvg-2.40)))
        ("libxpm" ,libxpm)
        ("libxml2" ,libxml2)
        ("libice" ,libice)

gnu/packages/gtk.scm

@@ -862,7 +862,10 @@ is part of the GNOME accessibility project.")
     (outputs '("out" "bin" "doc" "debug"))
     (propagated-inputs
      (list atk cairo
-           (librsvg-for-system) glib pango))
+           (if (target-x86-64?)
+             librsvg-bootstrap
+             librsvg-2.40)
+           glib pango))
     (inputs
      (list cups
            libx11
@@ -958,7 +961,9 @@ application suites.")
            fribidi
            fontconfig
            freetype
-           (librsvg-for-system)
+           (if (target-x86-64?)
+             librsvg-bootstrap
+             librsvg-2.40)
            glib
            libcloudproviders-minimal
            libepoxy