Darwin compilers default to PIC on, so -mdynamic-no-pic (which disables it 
again) needs to be added to cflags before enable pic is checked.

Fixes compilation without --enable-shared at least the 10.6 system compiler
for x86-32.
Fixes speed regression on all darwin arches except x86-64.


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@22730 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b