Add csrtool to view and change CSR registers

overlay.nix

@@ -37,6 +37,22 @@ final: prev:
     '';
   };
 
+  csrtool = prev.pkgsStatic.stdenv.mkDerivation {
+    name = "csrtool";
+    src = ./csrtool.c;
+    unpackPhase = ''
+      cp ${./csrtool.c} csrtool.c
+    '';
+    dontConfigure = true;
+    buildPhase = ''
+      $CC -static csrtool.c -o csrtool
+    '';
+    installPhase = ''
+      mkdir -p $out/bin
+      cp csrtool $out/bin/
+    '';
+  };
+
   bitstreams = builtins.fetchGit {
     url = "git@bscpm03.bsc.es:rarias/bitstreams.git";
     rev = "ad901b0c21ffbdb310ff1dfb269f169f6ac6bde6";