icon-conv-tools: init at 0.0.0 (#13905)

A nix specific set of tools for converting icon files
that are not in a freedesktop ready format.

I plan on using these tools for both `keepass` and
`retroarch` packages. It may benifit many other packages.

pkgs/build-support/icon-conv-tools/default.nix

@@ -0,0 +1,31 @@
+{ stdenv, icoutils }:
+
+stdenv.mkDerivation {
+  name = "icon-conv-tools-0.0.0";
+
+  src = ./.;
+
+  buildInputs = [ icoutils ];
+
+  patchPhase = ''
+    substituteInPlace "./bin/extractWinRscIconsToStdFreeDesktopDir.sh" \
+      --replace "icotool" "${icoutils}/bin/icotool" \
+      --replace "wrestool" "${icoutils}/bin/wrestool"
+  '';
+
+  buildPhase = ''
+    mkdir -p "$out/bin"
+    cp -p "./bin/"* "$out/bin"
+  '';
+
+  installPhase = "true";
+  
+  dontPatchELF = true;
+  dontStrip = true;
+
+  meta = {
+    description = "Tools for icon conversion specific to nix package manager";
+    maintainers = with stdenv.lib.maintainers; [ jraygauthier ];
+  };
+
+}