Invalid `SHELL` in `Makefile` for AIX builds?

Bug report

Bug description:

When trying to build CPython on AIX, the make steps fails immediately with the following error message:

$ ./configure
[...]
$ make       
/bin/sh -e: not found

make: 1254-004 The error code from the last command is 1.


Stop.

AIX make(1) interprets whatever is assigned to the SHELL variable as a file path to the shell. It thus tries to use a shell named "/bin/sh -e":

execve("/bin/sh -e", 0x0000000110004D28, 0x0FFFFFFFFFFFFB90) Err#2  ENOENT

The -e was added by #100220, however I wonder if this is the right approach.

Going by POSIX I think -e should be the default unless it is explicitly disabled:

The execution line shall then be executed by a shell as if it were passed as the argument to the system() interface, except that if errors are not being ignored then the shell -e option shall also be in effect. If errors are being ignored for the command (as a result of the -i option, a '-' command prefix, or a .IGNORE special target), the shell -e option shall not be in effect.

I assume the -e was added for GNU make, which does not set -e unless it is set to POSIX-conforming mode (GNU make: Choosing the shell).

If the Makefile is defined to be a POSIX Makefile, wouldn't it be better to define .POSIX: in the makefile?

Quick test with GNU make:

$ cat Makefile
.POSIX:

SHELL = /bin/sh

test:
	false; echo after false
$ make --version
GNU Make 4.4.1
Built for powerpc64le-unknown-linux-musl
Copyright (C) 1988-2023 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ make test
false; echo after false
make: *** [Makefile:4: test] Error 1

CPython versions tested on:

CPython main branch

Operating systems tested on:

Other

Linked PRs

• gh-149022

El issue apunta al Makefile y señala que -e fue añadido por #100220; empieza allí y compara el manejo de SHELL de AIX make con el comportamiento de POSIX citado. Reproduce el fallo en AIX o inspecciona el trabajo enlazado gh-149022; se indicará que se ha completado cuando el Makefile ya no pase una ruta de shell no válida a AIX make.