[PATCH] libstdc++: Override detection of flockfile support in newlib [PR123406]

[Hans-Peter Nilsson]

> From: Jonathan Wakely <jwakely@redhat.com>
> Date: Wed,  7 Jan 2026 11:49:15 +0000

> libstdc++-v3/ChangeLog:
> 
> 	PR libstdc++/123406
> 	* acinclude.m4 (GLIBCXX_CHECK_STDIO_LOCKING): Override detection
> 	of flockfile for non-cygwin newlib targets.
> 	* configure: Regenerate.
> ---
> 
> Tested x86_64-linux, where this doesn't change the generated c++config.h
> file.
> 
> Built on cris-elf to verify that the _GLIBCXX_USE_STDIO_LOCKING macro is
> no longer defined in c++config.h.

Thanks, this indeed fixes PR123406.  Tested against
r16-6493-ge77ba7ef8c75 for cris-elf.  IIUC there's some
"Tested-by:" git-footer I could add that'd fit, but we don't
use it so I don't bother to look up the correct speling.

brgds, H-P