Not entirely. I applied what you had for the autoconf section to my
configure, since I do not have autoconf installed in my environment. 

Specifically, this part of configure is what's messing with the build:

if test x$TARGET = xMIPS; then
  MIPS_TRUE=
  MIPS_FALSE='#'
else
  MIPS_TRUE='#'
  MIPS_FALSE=
fi

Since the target is being renamed to MIPS_LINUX or MIPS_IRIX, this test
assumes the target is not MIPS.

The patch you have gets past the build break, but doesn't actually
compile what I believe is a working libffi for MIPS.