AM_AUX_DIR_EXPAND incorrect on MacOS X: how to fix?

[Kyle F. Downey]

AM_AUX_DIR_EXPAND inserts this shell fragment:

am_aux_dir=`CDPATH=:; cd $ac_aux_dir && pwd`

which does not work properly on MacOS X 10.1. It improperly inserts a
newline at the end of the value. This trickles down to config.status,
where it results in a newline appearing in the sed script fragment for
symbols like ACLOCAL and AM_TAR, which breaks sed.

1) for autoconf 2.52, is there any work-around in configure.in that will
allow you to override this value?
2) for future versions, what's the best replacement shell fragment?

--kd