Clean up paraver derivations

pkgs/paraver/kernel.nix

@@ -1,5 +1,4 @@
-{
-  stdenv
+{ stdenv
 , fetchFromGitHub
 , autoreconfHook
 , boost
@@ -9,11 +8,16 @@
 , 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 +38,14 @@ 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}"