Clean up paraver derivations

pkgs/paraver/kernel.nix

@@ -1,19 +1,24 @@
 {
-  stdenv
-, fetchFromGitHub
-, autoreconfHook
-, boost
-, libxml2
-, xml2
-, autoconf
-, automake
-, pkg-config
-, zlib
+  stdenv,
+  fetchFromGitHub,
+  autoreconfHook,
+  boost,
+  libxml2,
+  xml2,
+  autoconf,
+  automake,
+  pkg-config,
+  zlib,
+
+  enableDebug ? false,
 }:
 
-stdenv.mkDerivation rec {
-  pname = "paraver-kernel";
+let
   version = "4.12.0";
+in
+stdenv.mkDerivation {
+  pname = "paraver-kernel";
+  inherit version;
 
   src = fetchFromGitHub {
     owner = "bsc-performance-tools";
@@ -34,10 +39,14 @@ stdenv.mkDerivation rec {
 
   dontStrip = true;
 
-  preConfigure = ''
-    export CFLAGS="-O3 -DPARALLEL_ENABLED"
-    export CXXFLAGS="-O3 -DPARALLEL_ENABLED"
-  '';
+  env =
+    let
+      flags = "-DPARALLEL_ENABLED " + (if enableDebug then "-ggdb -Og" else "-O3");
+    in
+    {
+      CFLAGS = flags;
+      CXXFLAGS = flags;
+    };
 
   configureFlags = [
     "--with-boost=${boost}"