[Cin] I tried to isolate x86 part of thirdparty mjpegtools from configure.ac

[Andrew Randrianasulu]

..but not sure if I did it correctly?

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## arch dep tests
ARCH=[`uname -m`]
I86=[`expr "x$ARCH" : 'xi[346]86.*'`]
X86=[`expr "x$ARCH" : 'x..._64*'`]



PKG_3RD([mjpegtools],[yes],
  [mjpegtools-2.1.0],
  [
if test "x$I86$X86" != "x00" ; then
   utils/mmxsse/.libs/libmmxsse.a \
fi
    utils/.libs/libmjpegutils.a \
    lavtools/.libs/liblavfile.a \
    lavtools/.libs/liblavjpeg.a \
    mplex/.libs/libmplex2.a \
    yuvfilters/.libs/libyuvfilters.a \
    mpeg2enc/.libs/libmpeg2encpp.a ],
  [ .  lavtools utils ])

based on x86 asm test below ....