sbcl, ecl, clisp: set meta.mainProgram

pkgs/development/compilers/ecl/default.nix

···
     description = "Lisp implementation aiming to be small, fast and easy to embed";
     homepage = "https://common-lisp.net/project/ecl/";
     license = licenses.mit;
+    mainProgram = "ecl";
     maintainers = lib.teams.lisp.members;
     platforms = platforms.unix;
     changelog = "https://gitlab.com/embeddable-common-lisp/ecl/-/raw/${version}/CHANGELOG";

pkgs/development/compilers/sbcl/default.nix

···
     description = "Common Lisp compiler";
     homepage = "https://sbcl.org";
     license = licenses.publicDomain; # and FreeBSD
+    mainProgram = "sbcl";
     maintainers = lib.teams.lisp.members;
     platforms = attrNames bootstrapBinaries ++ [
       # These aren’t bootstrapped using the binary distribution but compiled

pkgs/development/interpreters/clisp/default.nix

···
   meta = {
     description = "ANSI Common Lisp Implementation";
     homepage = "http://clisp.org";
+    mainProgram = "clisp";
     maintainers = lib.teams.lisp.members;
     license = lib.licenses.gpl2Plus;
     platforms = with lib.platforms; linux ++ darwin;