cppunit: disable blanket -Werror

`-Werror` flag usually causes build failures due to minor changes in
compiler versions. They might be useful for developers themselves but
are rarely useful for distributions.

For example right now `cppunit` fails to compile on `gcc-13` due to a
`gcc` infelicity: https://gcc.gnu.org/PR107488

While this concrete instance is a compiler bug generally `-Werror` makes
users' lives harder. Specific `-Werror=<foo>` are better way to prevent
certain classes of bugs.

The change removes planket `-Werror` with `--disable-werror` flag.

pkgs/development/libraries/cppunit/default.nix

@@ -9,6 +9,10 @@ stdenv.mkDerivation rec {
     sha256 = "19qpqzy66bq76wcyadmi3zahk5v1ll2kig1nvg96zx9padkcdic9";
   };
 
+  # Avoid blanket -Werror to evade build failures on less
+  # tested compilers.
+  configureFlags = [ "--disable-werror" ];
+
   meta = with lib; {
     homepage = "https://freedesktop.org/wiki/Software/cppunit/";
     description = "C++ unit testing framework";