The Ada compiler front-end of gcc is itself written
in Ada. Consequently, an Ada compiler must be used
to build this pkg. In pkgsrc, lang/gcc3-ada is version
3.3 of the gcc Ada compiler; it also requires an Ada
compiler to build. This pkg may also be built using
lang/gcc3 (which contains Ada).

You can download a pre-built version this package
(suitable for bootstrapping lang/gcc3) from: 

   http://www.johnrshannon.com/NetBSD/ix86/gccAda-3.4.0.tgz
   http://www.johnrshannon.com/NetBSD/pentium4/gccAda-3.4.0.tgz
   http://www.johnrshannon.com/NetBSD/x86_64/gccAda-3.4.0.tgz

The first two pkgs were built on NetBSD 2.0-BETA. The AMD64
pkg was built under NetBSD 1.6ZL.

Full Ada language support is provided for:
  Intel Ix86 on NetBSD with native pthread support
  AMD 64 on NetBSD with native pthread support

See comments in Makefile on selecting a bootstrap compiler.