Add flag for linker

component/ncurses/buildout.cfg

@@ -25,7 +25,7 @@ configure-options =
   --with-build-cc=$CC
   --with-build-cflags=$CFLAGS
   --with-build-cppflags=$CPPFLAGS
-  --with-build-ldflags=$LDFLAGS
+  --with-build-ldflags=D_GNU_SOURCE
 # tricky way to rerun with --enable-widec
 make-targets =
   install && (for i in curses unctrl eti form menu panel term; do ln -sf ncurses/$i.h @@LOCATION@@/include/$i.h; done; ln -sf libncurses.so @@LOCATION@@/lib/libcurses.so) && ./configure ${:configure-options} --enable-widec && make ${:make-options} && make ${:make-options} install