Make depot compile on Rasberry pi - will damage the sysroot approach

Hi,

I don't know how the majority is building omxplayer, but I find it feasable to use the Pi itself. Sadly a lot of things are not working if you use the RPi to compile omxplayer.

Please review the changes and let me know if this is OK, or what to be changed. I guess the best long term approach is
 - use ffmpeg as it comes from directly in Raspbian or from the system
 - swtich to automake and autoconf so that the configure system can detect which features can be enabled. With a proper autoconf environment doing a cross compilation, like how it's setup now per default with some Makefile.include can be done if desired