x265: Don't install static library

Following our general policy to only install dynamic libraries. If the
static library turns out to be needed, it could be moved to a separate
output.

pkgs/development/libraries/x265/default.nix

@@ -49,6 +49,10 @@ stdenv.mkDerivation rec {
     cd source
   '';
 
+  postInstall = ''
+    rm $out/lib/*.a
+  '';
+
   nativeBuildInputs = [ cmake yasm ];
 
   meta = with stdenv.lib; {