/bin/sh does not support "test -e", but configure runs itself with /bin/sh and then uses "test -e"
/bin/sh does support "test -f" however. Also systems which use bash for sh would work since it supports "test -e".
Thanks for the report, this problem is now fixed in the git repository.
To try it out, you either checkout/update your git clone: http://curl.haxx.se/source.html
or you try tomorrow's daily snapshot: http://curl.haxx.se/snapshots/