texlivePackages: add mainProgram to all packages with a single binary (#521238)

pkgs/tools/typesetting/tex/texlive/build-texlive-package.nix

@@ -84,10 +84,15 @@ let
   // lib.optionalAttrs hasCatalogue {
     homepage = "https://ctan.org/pkg/${catalogue}";
   }
-  // lib.optionalAttrs (args ? mainProgram) {
-    inherit (args) mainProgram;
+  // lib.optionalAttrs (mainProgram != null) {
+    inherit mainProgram;
   };
 
+  # if binfiles contains exactly one entry, use it as mainProgram, but allow overrides via args.mainProgram
+  mainProgram =
+    args.mainProgram
+      or (if builtins.length (args.binfiles or [ ]) == 1 then builtins.head args.binfiles else null);
+
   hasBinfiles = args ? binfiles && args.binfiles != [ ];
   hasDocfiles = sha512 ? doc;
   hasSource = sha512 ? source;

pkgs/tools/typesetting/tex/texlive/tlpdb-overrides.nix

@@ -636,6 +636,4 @@ lib.recursiveUpdate orig rec {
       fi
     '';
   };
-
-  texcount.mainProgram = "texcount";
 }