Build specinvoke from source

The one contained in the CPU SPEC ISO is built for x86, and there is no
binary for RISC-V.

overlay.nix

@@ -14,6 +14,7 @@ final: prev:
   spec-cpu-tools = final.callPackage ./pkgs/spec-cpu/tools.nix { };
   spec-cpu = final.callPackage ./pkgs/spec-cpu/default.nix { };
   spec-cpu-mini = final.callPackage ./pkgs/spec-cpu/mini.nix { };
+  specinvoke = final.callPackage ./pkgs/spec-cpu/specinvoke.nix { };
   spec-cpu-clang = final.callPackage ./pkgs/spec-cpu/default.nix { stdenv = final.stdenvClangEpi; };
 
   blis = ((prev.blis.override {

pkgs/spec-cpu/mini.nix

@@ -2,6 +2,7 @@
   stdenv
 , spec-cpu
 , spec-cpu-tools
+, specinvoke
 }:
 
 stdenv.mkDerivation rec {
@@ -49,9 +50,8 @@ stdenv.mkDerivation rec {
     mkdir -p $out/bin
     echo -e "#!$SHELL\necho $out" > $out/bin/spec-cpu-mini
     chmod +x $out/bin/spec-cpu-mini
-    cp $(command -v specinvoke) $out/bin
+    cp ${specinvoke}/bin/specinvoke $out/bin
   '';
-  nativeBuildInputs = [ spec-cpu-tools ];
   enableParallelBuilding = false;
   hardeningDisable = [ "all" ];
   dontStrip = true;

pkgs/spec-cpu/specinvoke.nix

@@ -0,0 +1,30 @@
+{
+  stdenv
+, libarchive
+, spec-cpu-tools
+, runCommandNoCC
+}:
+
+let
+  version = spec-cpu-tools.version;
+  tar = runCommandNoCC "specinvoke-${version}.tar" {
+    src = spec-cpu-tools.src;
+    nativeBuildInputs = [ libarchive ];
+  } ''
+    mkdir iso
+    bsdtar -C iso -xf $src
+    cp iso/install_archives/tools-src.tar $out
+  '';
+in stdenv.mkDerivation {
+  pname = "specinvoke";
+  version = version;
+  src = tar;
+  sourceRoot = "tools/src/specinvoke/";
+  # Almost no bugs
+  preInstall = ''
+    mkdir -p $out/bin
+  '';
+  enableParallelBuilding = false;
+  hardeningDisable = [ "all" ];
+  dontStrip = true;
+}