FLAT objects cannot have multiple sections, so using the L1 attributes breaks

FLAT objects cannot have multiple sections, so using the L1 attributes breaks
linking. The FDPIC relocs also break for any other format. Thus check the
compiler environment and select the appropriate sections/relocs.
patch by Mike Frysinger, vapier.adi a gmail d com

Originally committed as revision 12125 to svn://svn.ffmpeg.org/ffmpeg/trunk