makeDBusConf: Look for .conf files in share/dbus-1/system.d/ too

Some packages install their dbus config files to `share/dbus-1/system.d` instead
of `etc/dbus-1/system.d`, so look in both places.

pkgs/development/libraries/dbus/make-system-conf.xsl

···
       <xsl:for-each select="str:tokenize($serviceDirectories)">
         <servicedir><xsl:value-of select="." />/share/dbus-1/system-services</servicedir>
         <includedir><xsl:value-of select="." />/etc/dbus-1/system.d</includedir>
+        <includedir><xsl:value-of select="." />/share/dbus-1/system.d</includedir>
       </xsl:for-each>
     </busconfig>
   </xsl:template>