tv iosevka-tv-1: allow using prebuilt font

tv/5pkgs/override/iosevka-tv-1.nix

@@ -0,0 +1,26 @@
+self: super:
+
+let
+  prebuilt =
+    self.stdenv.mkDerivation rec {
+      pname = "iosevka-tv-1";
+      version = "15.6.3";
+      src = self.fetchurl {
+        urls = [
+          "https://c.krebsco.de/iosevka-tv-1-${version}.tar.gz"
+          "https://ni.krebsco.de/~tv/mirrors/iosevka/iosevka-tv-1-${version}.tar.gz"
+        ];
+        sha256 = "0shsvlb1cmn39l33nzd5bj8g0h9jg7rdq8hvlac8qvnzfhpi5s6k";
+      };
+      installPhase = ''
+        mkdir -p $out/share/fonts/truetype
+        mv -v *.ttf $out/share/fonts/truetype
+      '';
+    };
+in
+
+if super.iosevka.version == prebuilt.version then
+  prebuilt
+
+else
+  super.iosevka