qcachegrind: pin to Qt 5.6 and correct packaging errors

pkgs/development/tools/analysis/qcachegrind/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, cmake, qt, qmakeHook, makeQtWrapper, perl, python, php }:
+{ stdenv, fetchurl, cmake, qmakeHook, makeQtWrapper, qtbase, perl, python, php }:
 
 stdenv.mkDerivation rec {
   name = "qcachegrind-${version}";
@@ -9,7 +9,7 @@ stdenv.mkDerivation rec {
     sha256 = "109y94nz96izzsjjdpj9c6g344rcr86srp5w0433mssbyvym4x7q";
   };
 
-  buildInputs = [ qt.qtbase perl python php ];
+  buildInputs = [ qtbase perl python php ];
 
   nativeBuildInputs = [ qmakeHook makeQtWrapper ];
 

pkgs/top-level/all-packages.nix

@@ -6955,9 +6955,7 @@ with pkgs;
 
   valkyrie = callPackage ../development/tools/analysis/valkyrie { };
 
-  qcachegrind = libsForQt57.callPackage ../development/tools/analysis/qcachegrind {
-    qt = qt57;
-  };
+  qcachegrind = libsForQt56.callPackage ../development/tools/analysis/qcachegrind {};
 
   verasco = ocaml-ng.ocamlPackages_4_02.verasco.override {
     coq = coq_8_4;