Make sure the system on which GNAT is installed is accessible from the current machine, i.e., the install location is shared over the network. Shared resources are accessed on Windows by means of UNC paths, which have the format \\server\sharename\path
In order to use such a network installation, simply add the UNC path of the
bin directory of your GNAT installation in front of your PATH. For
example, if GNAT is installed in \GNAT directory of a share location
called c-drive on a machine LOKI, the following command will
make it available:
$ path \\loki\c-drive\gnat\bin;%path%`
Be aware that every compilation using the network installation results in the transfer of large amounts of data across the network and will likely cause serious performance penalty.