treewide: Add meta.mainProgram

This should fix most warnings getExe in based on grepping `nixos/`.

pkgs/applications/audio/espeak-ng/default.nix

···
     license = licenses.gpl3Plus;
     maintainers = with maintainers; [ aske ];
     platforms = platforms.all;
+    mainProgram = "espeak-ng";
   };
 }

pkgs/applications/display-managers/greetd/regreet.nix

···
     license = licenses.gpl3Plus;
     maintainers = with maintainers; [ fufexan ];
     platforms = platforms.linux;
+    mainProgram = "regreet";
   };
 }

pkgs/applications/emulators/darling/default.nix

···
     license = licenses.gpl3Plus;
     maintainers = with maintainers; [ zhaofengli ];
     platforms = [ "x86_64-linux" ];
+    mainProgram = "darling";
   };
 }

pkgs/applications/graphics/tesseract/tesseract5.nix

···
     license = lib.licenses.asl20;
     maintainers = with lib.maintainers; [ anselmschueler ];
     platforms = lib.platforms.unix;
+    mainProgram = "tesseract";
   };
 }

pkgs/applications/networking/browsers/firefox/packages.nix

···
                                              # not in `badPlatforms` because cross-compilation on 64-bit machine might work.
       maxSilent = 14400; # 4h, double the default of 7200s (c.f. #129212, #129115)
       license = lib.licenses.mpl20;
+      mainProgram = "firefox";
     };
     tests = [ nixosTests.firefox ];
     updateScript = callPackage ./update.nix {
···
                                              # not in `badPlatforms` because cross-compilation on 64-bit machine might work.
       maxSilent = 14400; # 4h, double the default of 7200s (c.f. #129212, #129115)
       license = lib.licenses.mpl20;
+      mainProgram = "firefox";
     };
     tests = [ nixosTests.firefox-beta ];
     updateScript = callPackage ./update.nix {
···
                                              # not in `badPlatforms` because cross-compilation on 64-bit machine might work.
       maxSilent = 14400; # 4h, double the default of 7200s (c.f. #129212, #129115)
       license = lib.licenses.mpl20;
+      mainProgram = "firefox";
     };
     tests = [ nixosTests.firefox-devedition ];
     updateScript = callPackage ./update.nix {
···
       broken = stdenv.buildPlatform.is32bit; # since Firefox 60, build on 32-bit platforms fails with "out of memory".
                                              # not in `badPlatforms` because cross-compilation on 64-bit machine might work.
       license = lib.licenses.mpl20;
+      mainProgram = "firefox";
     };
     tests = [ nixosTests.firefox-esr-102 ];
     updateScript = callPackage ./update.nix {
···
       broken = stdenv.buildPlatform.is32bit; # since Firefox 60, build on 32-bit platforms fails with "out of memory".
                                              # not in `badPlatforms` because cross-compilation on 64-bit machine might work.
       license = lib.licenses.mpl20;
+      mainProgram = "firefox";
     };
     tests = [ nixosTests.firefox-esr-115 ];
     updateScript = callPackage ./update.nix {

pkgs/applications/networking/clash-verge/default.nix

···
     license = licenses.gpl3Plus;
     sourceProvenance = with sourceTypes; [ binaryNativeCode ];
     maintainers = with maintainers; [ zendo ];
+    mainProgram = "clash-verge";
   };
 }

pkgs/applications/networking/irc/thelounge/default.nix

···
     maintainers = with maintainers; [ winter raitobezarius ];
     license = licenses.mit;
     inherit (nodejs.meta) platforms;
+    mainProgram = "thelounge";
   };
 })

pkgs/applications/version-management/gitea/default.nix

···
     license = licenses.mit;
     maintainers = with maintainers; [ disassembler kolaente ma27 techknowlogick ];
     broken = stdenv.isDarwin;
+    mainProgram = "gitea";
   };
 }

pkgs/applications/window-managers/cage/default.nix

···
     license     = licenses.mit;
     platforms   = platforms.linux;
     maintainers = with maintainers; [ primeos ];
+    mainProgram = "cage";
   };
 }

pkgs/development/libraries/xdg-dbus-proxy/default.nix

···
     license = licenses.lgpl21Plus;
     maintainers = with maintainers; [ jtojnar ];
     platforms = platforms.linux;
+    mainProgram = "xdg-dbus-proxy";
   };
 }

pkgs/development/tools/continuous-integration/woodpecker/agent.nix

···
 
   meta = common.meta // {
     description = "Woodpecker Continuous Integration agent";
+    mainProgram = "woodpecker-agent";
   };
 }

pkgs/development/tools/continuous-integration/woodpecker/server.nix

···
 
   meta = common.meta // {
     description = "Woodpecker Continuous Integration server";
+    mainProgram = "woodpecker-server";
   };
 }

pkgs/development/tools/geckodriver/default.nix

···
     homepage = "https://github.com/mozilla/geckodriver";
     license = licenses.mpl20;
     maintainers = with maintainers; [ jraygauthier ];
+    mainProgram = "geckodriver";
   };
 }

pkgs/development/tools/selenium/chromedriver/default.nix

···
     # Note from primeos: By updating Chromium I also update Google Chrome and
     # ChromeDriver.
     platforms = attrNames allSpecs;
+    mainProgram = "chromedriver";
   };
 }

pkgs/os-specific/linux/below/default.nix

···
     description = "A time traveling resource monitor for modern Linux systems";
     license = licenses.asl20;
     homepage = "https://github.com/facebookincubator/below";
+    mainProgram = "below";
   };
 }

pkgs/servers/code-server/default.nix

···
     license = lib.licenses.mit;
     maintainers = with lib.maintainers; [ offline henkery code-asher ];
     platforms = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" ];
+    mainProgram = "code-server";
   };
 })

pkgs/servers/consul/default.nix

···
     platforms = platforms.linux ++ platforms.darwin;
     license = licenses.mpl20;
     maintainers = with maintainers; [ pradeepchhetri vdemeester nh2 techknowlogick];
+    mainProgram = "consul";
   };
 }

pkgs/servers/dns/acme-dns/default.nix

···
     changelog = "https://github.com/joohoi/acme-dns/releases/tag/${src.rev}";
     license = lib.licenses.mit;
     maintainers = with lib.maintainers; [ emilylange ];
+    mainProgram = "acme-dns";
   };
 }

pkgs/servers/ldap/lldap/default.nix

···
     license = licenses.gpl3Only;
     platforms = platforms.linux;
     maintainers = with maintainers; [ emilylange bendlas ];
+    mainProgram = "lldap";
   };
 })

pkgs/servers/monitoring/grafana-agent/default.nix

···
     homepage = "https://grafana.com/products/cloud";
     changelog = "https://github.com/grafana/agent/blob/${src.rev}/CHANGELOG.md";
     maintainers = with lib.maintainers; [ flokli emilylange ];
+    mainProgram = "grafana-agent";
   };
 }

pkgs/servers/openvscode-server/default.nix

···
     license = lib.licenses.mit;
     maintainers = with lib.maintainers; [ dguenther ghuntley emilytrau ];
     platforms = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+    mainProgram = "openvscode-server";
   };
 })

pkgs/servers/pufferpanel/default.nix

···
     homepage = "https://www.pufferpanel.com/";
     license = with licenses; [ asl20 ];
     maintainers = with maintainers; [ ckie tie ];
+    mainProgram = "pufferpanel";
   };
 }

pkgs/servers/web-apps/kavita/default.nix

···
     license = lib.licenses.gpl3Only;
     platforms = lib.platforms.linux;
     maintainers = with lib.maintainers; [ misterio77 ];
+    mainProgram = "kavita";
   };
 })

pkgs/servers/x11/xorg/overrides.nix

···
         --replace '_X_NORETURN' '__attribute__((noreturn))' \
         --replace 'n_dirs--;' ""
     '';
+    meta.mainProgram = "lndir";
   });
 
   twm = super.twm.overrideAttrs (attrs: {

pkgs/tools/backup/tarsnap/default.nix

···
     license     = lib.licenses.unfree;
     platforms   = lib.platforms.unix;
     maintainers = with lib.maintainers; [ thoughtpolice roconnor ];
+    mainProgram = "tarsnap";
   };
 }

pkgs/tools/misc/direnv/default.nix

···
     homepage = "https://direnv.net";
     license = licenses.mit;
     maintainers = teams.numtide.members;
+    mainProgram = "direnv";
   };
 }

pkgs/tools/misc/vector/default.nix

···
     license = licenses.mpl20;
     maintainers = with maintainers; [ thoughtpolice happysalada ];
     platforms = with platforms; all;
+    mainProgram = "vector";
   };
 }

pkgs/tools/networking/clash-meta/default.nix

···
     homepage = "https://github.com/MetaCubeX/Clash.Meta";
     license = licenses.gpl3Only;
     maintainers = with maintainers; [ oluceps ];
+    mainProgram = "clash-meta";
   };
 }

pkgs/tools/networking/clash/default.nix

···
     changelog = "https://github.com/Dreamacro/clash/releases/tag/v${version}";
     license = licenses.gpl3Only;
     maintainers = with maintainers; [ contrun Br1ght0ne ];
+    mainProgram = "clash";
   };
 }

pkgs/tools/networking/sitespeed-io/default.nix

···
     license = licenses.mit;
     maintainers = with maintainers; [ misterio77 ];
     platforms = lib.unique (geckodriver.meta.platforms ++ chromedriver.meta.platforms);
+    mainProgram = "sitespeed-io";
   };
 }

pkgs/tools/networking/wgautomesh/default.nix

···
     homepage = "https://git.deuxfleurs.fr/Deuxfleurs/wgautomesh";
     license = licenses.agpl3Only;
     maintainers = [ maintainers.lx ];
+    mainProgram = "wgautomesh";
   };
 }

pkgs/tools/package-management/harmonia/default.nix

···
     homepage = "https://github.com/nix-community/harmonia";
     license = licenses.mit;
     maintainers = with maintainers; [ mic92 ];
+    mainProgram = "harmonia";
   };
 }

pkgs/tools/system/auto-cpufreq/default.nix

···
     license = licenses.lgpl3Plus;
     platforms = platforms.linux;
     maintainers = [ maintainers.Technical27 ];
+    mainProgram = "auto-cpufreq";
   };
 }

pkgs/tools/system/kanata/default.nix

···
     license = licenses.lgpl3Only;
     maintainers = with maintainers; [ linj ];
     platforms = platforms.linux;
+    mainProgram = "kanata";
   };
 }