Yasm required to build ffmpeg for arch=i386

[bruno.herbelin@…]

Compilation of port ffmpeg fails if macport build_arch is i386 (on a x86_64 machine): It is not a C error, but a gcc asm problem; " ‘asm’ operand has impossible constraints " (i don't remember which file, but it was in libavcodec).

To fix this, I added --enable-yasm to the list of configure.args in the Portfile of ffmpeg.

Of course, yasm should also be added as a dependency to ffmpeg. I would recommend to enable yasm for all architecture (no need to make different behavior between 32 and 64 bits).

Thanks for the good work with macports !

PS: this is not the same as Ticket #30137, but related ?