set main module name for escript

Index: rebar.config
--- rebar.config.orig
+++ rebar.config
@@ -12,7 +12,7 @@
 {escript_name, rebar3}.
 {escript_wrappers_windows, ["cmd", "powershell"]}.
 {escript_comment, "%%Rebar3 3.22.1\n"}.
-{escript_emu_args, "%%! +sbtu +A1\n"}.
+{escript_emu_args, "%%! +sbtu +A1 -escript main rebar3\n"}.
 %% escript_incl_priv is for internal rebar-private use only.
 %% Do not use outside rebar. Config interface is not stable.
 {escript_incl_priv, [{relx, "templates/*"},