Ada: problem with use of $(srcdir) in ada Makefiles

[Graham Stott]

All,

While building a mips-unknown-elf cross compiler I encountered
a problem with the generated Ada Makefile (i.e gcc/ada/Makefile)
using srcdir to refer to the gcc/ada directory.

The problem here is in the rest of the build machinery srcdir is
the gcc directory so when we want to refer to a file such as
gcc/config/mips/ecoff.h in makefile we use $(srcdir)/config/mips/ecoff.h
which won't work in the ada Makefiles because srcdir is gcc/ada.

I think the Ada Makefile.in needs to change so that it conforms
to the standard usage for srcdir. 

Graham