cuneiform: Fix build against glibc 2.26

Since glibc 2.26 the string.h file includes <strings.h>, which in case
of cuneiform will include the strings.h found in Kern/hhh/tigerh/h,
because of the search path order.

Fortunately for us the strings.h in cuneiform are completely unused and
no files reference or include it. I even checked various references to
types within strings.h and the only occurences are in cf_strings.h,
which is also included by other files.

Signed-off-by: aszlig <aszlig@nix.build>
Cc: @7c6f434c

pkgs/tools/graphics/cuneiform/default.nix

@@ -16,6 +16,10 @@ stdenv.mkDerivation rec {
   })
   ];
 
+  postPatch = ''
+    rm cuneiform_src/Kern/hhh/tigerh/h/strings.h
+  '';
+
   buildInputs = [ imagemagick ];
 
   nativeBuildInputs = [ cmake ];