bug#79385: build: don't force specific warning options on gnulib code

[Paul Eggert]

On 2025-09-03 18:38, Bruno Haible wrote:

What circumstances are these?

As detailed in
<https://lists.gnu.org/archive/html/bug-gnulib/2025-09/msg00033.html>:

   $ ./configure --enable-gcc-warnings
   $ make CFLAGS='-g -O2' V=1

But that bug report is about vma-iter, which grep doesn't use.