Hi,
which distribution is installed ?
You might be able to do that without the need of executing "make install".
But you in order to get a shared gd extension you need to use the switch
--with-gd=shared
After compilation you'll have a shared gd extension file (something like gd.so).
Copy that file to the directory that is set as extension_dir in php.ini and add e.g. extension=gd.so to php.ini. Then restart the web server.