[Bug ada/64492] Disabling libada prevents building gnattools-cross

["laguest at archeia dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64492

--- Comment #11 from Luke A. Guest <laguest at archeia dot com> ---
(In reply to simon from comment #5)
> (In reply to Luke A. Guest from comment #2)
> > But, I noticed this in the gnat makefile a while back and was going to
> > investigate, but haven't got around to it yet:
> > 
> > # *-elf, *-eabi, or *-eabispe
> > ifeq ($(strip $(filter-out elf eabi eabispe,$(target_os))),)
> >   TOOLS_TARGET_PAIRS=\
> >   mlib-tgt-specific.adb<mlib-tgt-specific-xi.adb \
> >   indepsw.adb<indepsw-gnu.adb
> > endif
> > 
> > Essentially, we just need for that to include a specific system or build
> > with just those two files and it's sorted.
> 
> I agree that, for some reason, this tools target pair is not actioned for
> target arm-eabi. Perhaps there should be another PR?
> 

No, in my patch above, you only have part of the patch, the second part adds
the necessary lines in the gnattools/configure script to enable them correctly
including lib support. Without that it shouldn't even build but if it does by
some miracle it will use defaults which are very basic.

> The effect is that arm-eabi-gnatmake is unable to build libraries on this
> platform. However, gprbuild is OK. I always use gprbuild when building
> libraries because it does a much better job, and is necessary when building
> Darwin dylibs.
> 
> I understand (canât remember where from) that AdaCore intend to remove the
> ability of gnatmake to build libraries for any target in future releases. If
> this is true, I think it would be regrettable, since gprbuild isnât part of
> GCC (it does have copyright assignment to FSF, though). GCC 5 is still OK.

Well that's a stupid idea,