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

["simon at pushface dot org" <gcc-bugzilla at gcc dot gnu dot org>]

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

--- Comment #5 from simon at pushface dot org ---
(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?

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.