sdcc: use nativeBuildInputs

Ref https://github.com/jtojnar/nixpkgs-hammering/blob/master/explanations/build-tools-in-build-inputs.md

pkgs/development/compilers/sdcc/default.nix

···
     sha256 = "042fxw5mnsfhpc0z9lxfsw88kdkm32pwrxacp88kj2n2dy0814a8";
   };
 
-  buildInputs = [ autoconf bison boost flex gputils texinfo zlib ];
+  buildInputs = [ boost gputils texinfo zlib ];
+
+  nativeBuildInputs = [ autoconf bison flex ];
 
   configureFlags = map (f: "--disable-${f}-port") excludedPorts;