libxcrypt: prevent build failure on warnings

The upstream autoconf build system has a default setting that treats
compiler warnings as errors. While this can be useful for development
and maintenance it's not ideal for packaging and distribution: newer
versions of compilers may detect warnings that previous versions of the
compilers failed to detect and cause this package to fail to build.

pkgs/development/libraries/libxcrypt/default.nix

@@ -16,6 +16,10 @@ stdenv.mkDerivation rec {
     ./autogen.sh
   '';
 
+  configureFlags = [
+    "--disable-werror"
+  ];
+
   nativeBuildInputs = [ autoconf automake libtool pkg-config perl ];
 
   doCheck = true;