That error is because you don't have libfixposix installed on your machine. Â libfixposix is a library being written by Stelian Ionescu, the author of IOLib, to unify some POSIX behavior across various unix machines. It is a C library which is compiled and installed seperately from IOLib or any other Common Lisp installation.
It is found here: http://gitorious.org/libfixposix/libfixposix
You can get a copy of it by: git clone git://gitorious.org/libfixposix/libfixposix.git
Then make && make install as root.
Afterwards, the build of IOLib in SBCL should work.
it's more complicated, see the README in libfixposix.
also, i'd recommend adding this section to the README of iolib:
* Dependencies IOLib depends on a library called libfixposix available at (http://gitorious.org/libfixposix/libfixposix). It's a C library meant to unify POSIX behavior across various unix machines, and it needs to be compiled and installed seperately from IOLib.
git clone git://gitorious.org/libfixposix/libfixposix.git
Follow its instruction about the install procedure.