Bug#1067453: gnat: Ada.Calendar.Clock crashes on time_t64 architectures

[Nicolas Boulenguez <nicolas@debian.org>]

Source: gcc-13
Followup-For: Bug #1067453

Sorry for the poor summary. Here is what I have built and tested.
 * native build on ppc46el (not amd64)
 * gcc-source 13.2.0-19 from Debian
 * libgnat-timet64.diff unapplied
   (pr114065-proposed.diff should be unapplied for -20 and later)
 * commits 1/8 to 8/8 from bug114065attempt3.tar.gz applied
   (Debian only needs 1-3, 4-8 should only affect style).
 * ada-lib-info-source-date-epoch.diff adapted as described in #1067453
   (disabling it for a while is also an option)
 * debian/rules binary-arch

cat > demo.adb <<EOF
with Ada.Calendar; use Ada.Calendar;
with Ada.Text_IO;  use Ada.Text_IO;
procedure Demo is
   Y : Year_Number;
   M : Month_Number;
   D : Day_Number;
   S : Day_Duration;
begin
   Split (Clock, Y, M, D, S);
   Put_Line (Y'Img & M'Img & D'Img & S'Img);
end Demo;
EOF

ARCH=powerpc64le-linux-gnu
LD_LIBRARY_PATH=debian/tmp/usr/lib/gcc/$ARCH/13/adalib \
  debian/tmp/usr/bin/$ARCH-gnatmake-13 demo.adb \
  --RTS=debian/tmp/usr/lib/gcc/$ARCH/13 \
  --GNATBIND=debian/tmp/usr/bin/$ARCH-gnatbind-13 \
  --GNATLINK=debian/tmp/usr/bin/$ARCH-gnatlink-13

LD_LIBRARY_PATH=build/gcc/ada/rts ./demo
# should report the date