libraries/agg: disable building of examples to fix build

Previously the build was failing with due to not being able to find
libexamples.la.

pkgs/development/libraries/agg/default.nix

@@ -16,7 +16,7 @@ stdenv.mkDerivation rec {
     sh autogen.sh
   '';
 
-  configureFlags = "--x-includes=${libX11.dev}/include --x-libraries=${libX11.out}/lib";
+  configureFlags = "--x-includes=${libX11.dev}/include --x-libraries=${libX11.out}/lib --enable-examples=no";
 
   # libtool --tag=CXX --mode=link g++ -g -O2 libexamples.la ../src/platform/X11/libaggplatformX11.la ../src/libagg.la -o alpha_mask2 alpha_mask2.o
   # libtool: error: cannot find the library 'libexamples.la'