You do not provide info on how you try to build the plugin. The buildsystem currently by the git is set up a bit weird at the moment because I have not finshed testing the plugin yet.
If you build enigma2 diff3 or higher, the buildsystem will let you select the player you want. With diff0 or diff2 you can select a player, but in lines 384 through 387 of make.sh this is overridden to buildinplayer. As a result the system should build a playerless enigma2 without the plugin.
When you comment the lines out, the various variants of the plugin can be built and on my system they indeed compile without errors. Please note that the order in which things are built is changed: gstreamer and its plugins and sinks for instance are built after enigma2, not before it as with diff3 and higher.
However the image bult still refuses to start due to gst-symbols it cannot resolve. I am busy solving that.
Regards,
Audioniek.