Please consider to update libtool before the next release.
The current libtool files are very old in between and are from 2 different
libtool versions: While ltmain.sh is from 1.5.22, libtool.m4 is from an older
than 1.5.22 version. I'm using libgcrypt on interix, and unfortunately, the
first libtool version supporting interix is 1.5.22. So please update at least
to 1.5.24 as this can handle even newer interix versions as well.