rebuild libdmtx and librsvg if libpng so version has changed.

component/libdmtx/buildout.cfg

@@ -6,6 +6,7 @@ extends =
   ../bzip2/buildout.cfg
   ../imagemagick/buildout.cfg
   ../jbigkit/buildout.cfg
+  ../libpng/buildout.cfg
   ../zlib/buildout.cfg
 parts =
   libdmtx
@@ -22,6 +23,8 @@ configure-options =
 recipe = slapos.recipe.cmmi
 url = http://prdownloads.sourceforge.net/libdmtx/dmtx-utils-0.7.4.tar.bz2
 md5sum = b132ab9fb1d289869469b8bb4959a08a
+depends =
+  ${libpng:so_version}
 configure-options =
   --disable-static
 environment =

component/librsvg/buildout.cfg

@@ -3,6 +3,7 @@ parts = librsvg
 extends =
   ../bzip2/buildout.cfg
   ../pkgconfig/buildout.cfg
+  ../libpng/buildout.cfg
   ../libxml2/buildout.cfg
   ../zlib/buildout.cfg
   ../gtk-2/buildout.cfg
@@ -23,6 +24,8 @@ recipe = slapos.recipe.cmmi
 version = 2.36.1
 url = http://ftp.gnome.org/pub/GNOME/sources/librsvg/2.36/librsvg-2.36.4.tar.xz
 md5sum = 3c94524c8ccf668e30b236f409239f54
+depends =
+  ${libpng:so_version}
 configure-options =
   --disable-static
   --disable-gtk-theme