stack/erp5: add ghostscript to PATH of zopes

This will be used to do OCR from PDF documents

stack/erp5/buildout.cfg

@@ -7,6 +7,7 @@ extends =
   buildout.hash.cfg
   ../../component/fonts/buildout.cfg
   ../../component/git/buildout.cfg
+  ../../component/ghostscript/buildout.cfg
   ../../component/graphviz/buildout.cfg
   ../../component/gzip/buildout.cfg
   ../../component/xz-utils/buildout.cfg
@@ -250,6 +251,7 @@ link-binary =
   ${graphviz:location}/bin/dot
   ${grep:location}/bin/grep
   ${imagemagick:location}/bin/convert
+  ${ghostscript:location}/bin/gs
   ${imagemagick:location}/bin/identify
   ${jpegoptim:location}/bin/jpegoptim
   ${jsl:location}/bin/jsl