Gnat 3.07 undefined reference?

[njt@minster.york.ac.uk (Nigel J. Tracey)]

I am trying to compile the gnatf tool for linux using
the gnat 3.07 source and gcc 2.7.2.1. I have followed
the instructions in the various files from gnat and
gcc and all compiles fine until the linking stage when
I get the error 

a-raise.o: In function `__gnat_raise_nodefer_with_msg'
/usr/src/gcc-2.7.2.1/ada/a-raise.c:104:
			undefined reference to `__builtin_longjmp'

I really want to be able to use the gnat front-end to
build the AST and perform the semantic checks and
I then want to be able to use the decorated AST
to walk around it to extract various type and
parameter information for a automatic Ada test-case
data generation tool I'm working on. I thought
I would start simple and compile the gnatf tool
as this must use all the source that I will require.
But I can't get it to compile. Any help as to why
this reference is undefined would be a great help.

Thanks for any help
(Please CC replies to njt@minster.york.ac.uk - as our
news server is not very reliable here).

Nigel

--------------------
Nigel J. Tracey MEng, Research Associate (High Integrity Systems Group).
Department of Computer Science,   Office: X/D016
University of York,               Tel   : [0|+44]1904 432769
York, England.                    E-Mail: njt@minster.york.ac.uk
YO1 5DD.                          URL   : http://sv1pc161.cs.york.ac.uk/~njt