Unpack this tar file and read the README and Makefile. Install the library according to the instructions. Installation in /usr/local is strongly recommended since otherwise autoconf very likely won't be able to find it.
2) Make sure you have a copy of the 'gperf' tool. This does not come with the Mac OS X 10.1 developer tools, so you probably don't. You can check with:
% which gperf
If not found, grab a gperf source package and install it.
3) Configure, build and install the Icarus Verilog sources.
The only change you need to make here is to use a configure command like:
% CC="cc -no-cpp-precomp" ./configure
This assumes you are using 'sh', 'zsh', or 'bash'. If you are using 'csh' or 'tcsh', then you'll want something like: