writeShellApplication: set meta.mainProgram

pkgs/build-support/trivial-builders.nix

@@ -292,13 +292,16 @@ rec {
         ${text}
       '';
 
-      checkPhase = if checkPhase == null then ''
+      checkPhase =
+        if checkPhase == null then ''
           runHook preCheck
           ${stdenv.shell} -n $out/bin/${name}
           ${shellcheck}/bin/shellcheck $out/bin/${name}
           runHook postCheck
         ''
         else checkPhase;
+
+      meta.mainProgram = name;
     };
 
   # Create a C binary