build error: conflicting types for 'getenv'; have 'char *(void)'

Hi,

I'm the current maintainer of crosstool-ng. We had a bug report form a
user[1] with a configuration that involved building GNU make from
source.

I haven't been able to reproduce the error yet (the users on macOS,
I've tried a few different debian containers) but eye-balling the
latest source the problem still seems to be there[2] if I can trigger
the need to back-fill from gnulib.

It looks like others have hit a similar error[3] but that fix hasn't
been picked up (and I don't think it will address the one that the
ct-ng user reported).

I'll see if I can find a way of reproducing the issue and if I can,
the fix should be relatively straightforward.

Thanks,
Chris

[1] - https://github.com/crosstool-ng/crosstool-ng/issues/2446
[2] - https://cgit.git.savannah.gnu.org/cgit/make.git/tree/gl/lib/fnmatch.c#n122
[3] - https://lists.gnu.org/archive/html/bug-make/2025-03/msg00033.html