The FFMpeg can be made to build by OMK hackish way.

The directory
  _build/user/ffmpeg/libavcodec/x86
has to be created by hand. FFMpeg configure
has to be run in sources directory. It generates
config.h and config.mak there. generated config.mak
has to be included in config.omk or config.target
and next line has to be appended to that file
  CFLAGS+=-DHAVE_AV_CONFIG_H $(OPTFLAGS)
The line with LDFLAGS has to be commented out
and project has to be updated according to EXTRALIBS.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>