looking at
https://launchpadlibrarian.net/876718955/buildlog_ubuntu-stonking-amd64.gcc-mingw-w64_29_BUILDING.txt.gz

gcc: fatal error: cannot execute ‘gnat1’: posix_spawnp: No such file or
directory
compilation terminated.
gnatmake: "/<<PKGBUILDDIR>>/src/gcc/ada/gen_il-main.adb" compilation error
make[4]: *** [/<<PKGBUILDDIR>>/src/gcc/ada/Make-generated.in:13:
ada/stamp-gen_il] Error 4
make[4]: *** Waiting for unfinished jobs....
cp -p /<<PKGBUILDDIR>>/src/gcc/ada/snames.ads-tmpl
/<<PKGBUILDDIR>>/src/gcc/ada/snames.adb-tmpl
/<<PKGBUILDDIR>>/src/gcc/ada/snames.h-tmpl
/<<PKGBUILDDIR>>/src/gcc/ada/xsnamest.adb
/<<PKGBUILDDIR>>/src/gcc/ada/xutil.ads
/<<PKGBUILDDIR>>/src/gcc/ada/xutil.adb ada/bldtools/snamest
echo timestamp > s-i386-bt
cd ada/bldtools/snamest && gnatmake xsnamest && ./xsnamest
gcc -c xsnamest.adb
gcc: fatal error: cannot execute ‘gnat1’: posix_spawnp: No such file or
directory
compilation terminated.
gnatmake: "xsnamest.adb" compilation error
make[4]: *** [/<<PKGBUILDDIR>>/src/gcc/ada/Make-generated.in:41:
ada/stamp-snames] Error 4
yes

with GCC still defaulting to 15.  You assume that the GCC version
matches the version that you are building with.

Also I find the name for the target_version macro a bit confusing,
because it means both, the version for the target, and the version for
the build (the build still succeeds building with 15).

patch attached.

(This affects Ubuntu, not Debian currently.)

It’s a bit more complicated than that — the GCC build doesn’t allow suffixed
gnat binaries to be referenced, which is why gcc-mingw-w64 installs its own
unsuffixed links to gnat binaries; but then gnatmake assumes that unsuffixed
gcc can build Ada. This is new though, I’ve build gcc-mingw-w64 with
non-default gcc versions plenty of times in the past.

But your fix is correct, thanks!

It’s the version of GCC that the build targets; that is indeed confusing,
I’ll change it to gcc_version.

Regards,

Stephen

well, this still doesn't make the distinction between build and target
version. It's still possible to build gnat for 16 using gnat 15.