fna3d, r10k, xpipe: hardcoded meta.mainProgram (#428333)

pkgs/by-name/fn/fna3d/package.nix

@@ -33,7 +33,7 @@ stdenv.mkDerivation rec {
     homepage = "https://fna-xna.github.io/";
     license = lib.licenses.mspl;
     platforms = lib.platforms.linux;
-    mainProgram = pname;
+    mainProgram = "fna3d";
     maintainers = with lib.maintainers; [ mrtnvgr ];
   };
 }

pkgs/by-name/r1/r10k/package.nix

@@ -47,6 +47,6 @@ bundlerApp rec {
       anthonyroussel
     ];
     platforms = lib.platforms.unix;
-    mainProgram = pname;
+    mainProgram = "r10k";
   };
 }

pkgs/by-name/xp/xpipe/package.nix

@@ -153,6 +153,6 @@ stdenvNoCC.mkDerivation rec {
     ];
     maintainers = with lib.maintainers; [ crschnick ];
     platforms = [ "x86_64-linux" ];
-    mainProgram = pname;
+    mainProgram = "xpipe";
   };
 }