lambda-delta: fix build with clang

pkgs/applications/emulators/lambda-delta/default.nix

···
 
   nativeBuildInputs = [ autoreconfHook pkg-config ];
   buildInputs = [ SDL2 ];
+  env = lib.optionalAttrs stdenv.cc.isClang {
+    NIX_CFLAGS_COMPILE = "-std=c89";
+  };
+
 
   configureFlags = [ "--without-SDL1" ];