configure: make call to readlink portable to non-GNU (BSD) systems

The argument '-e' for readlink is a GNU extension.
In setting the variable 'where' the argument '-e' is not necessary, thus eliminated.

 reporter_name="Harold Grovesteen"

 reporter_url="http://sourceware.org/ml/crossgcc/2009-11/msg00052.html"

 reporter_comment=""