libiconv: add "enableShared" option

When false, shared libraries will be disabled.

also adds patch to *really* disable shared libiconv.

pkgs/development/libraries/libiconv/default.nix

@@ -1,6 +1,7 @@
 { fetchurl, stdenv, lib
 , buildPlatform, hostPlatform
 , enableStatic ? stdenv.hostPlatform.useAndroidPrebuilt
+, enableShared ? !stdenv.hostPlatform.useAndroidPrebuilt
 }:
 
 # assert !stdenv.isLinux || hostPlatform != buildPlatform; # TODO: improve on cross
@@ -23,10 +24,14 @@ stdenv.mkDerivation rec {
     lib.optionalString ((hostPlatform != buildPlatform && hostPlatform.libc == "msvcrt") || stdenv.cc.nativeLibc)
       ''
         sed '/^_GL_WARN_ON_USE (gets/d' -i srclib/stdio.in.h
-      '';
+      ''
+    + lib.optionalString (!enableShared) ''
+      sed -i -e '/preload/d' Makefile.in
+    '';
 
   configureFlags = lib.optional stdenv.isFreeBSD "--with-pic"
-    ++ lib.optional enableStatic "--enable-static";
+    ++ lib.optional enableStatic "--enable-static"
+    ++ lib.optional (!enableShared) "--disable-shared";
 
   meta = {
     description = "An iconv(3) implementation";