dump1090: fix html path

Use correct variable syntax for GNU Make so that HTML resources
can be found when running `dump1090 --net`. Additionally, add
view1090 binary to output.

pkgs/applications/misc/dump1090/default.nix

@@ -15,11 +15,11 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ libusb rtl-sdr ];
 
-  makeFlags = [ "PREFIX=$out" ];
+  makeFlags = [ "PREFIX=$(out)" ];
 
   installPhase = ''
     mkdir -p $out/bin $out/share
-    cp -v dump1090 $out/bin/dump1090
+    cp -v dump1090 view1090 $out/bin
     cp -vr public_html $out/share/dump1090
   '';