Use 'erlexec' directly to avoid overwriting the 'erl' executable

The main motivation is that on some installations the Erlang
executables are not writable, and the overwriting would fail.

The 'erl' script was initially created to fix escript,
but escript is no longer using it, so the entire script can be removed.

rebar.config

@@ -134,7 +134,6 @@
                    {copy, "tools/ssl/mongooseim/dh_server.pem",   "priv/ssl/fake_dh_server.pem"},
                    {copy, "tools/ssl/ca/cacert.pem",              "priv/ssl/cacert.pem"},
 
-                   {copy,     "rel/files/erl",          "erts-\{\{erts_vsn\}\}/bin/erl"},
                    %% Copy the whole directory scripts into scripts.
                    %% Still works, if the destination "scripts/" directory exists.
                    {copy, "rel/files/scripts",   "./"},

rel/files/mongooseimctl

@@ -27,6 +27,7 @@ MIM_DIR="${RUNNER_SCRIPT_DIR%/*}"
 EJABBERD_VMARGS_PATH="${RUNNER_ETC_DIR}"/vm.args
 START_ERL=`cat "$MIM_DIR"/releases/start_erl.data`
 ERTS_VSN="${START_ERL% *}"
+APP_VSN="${START_ERL#* }"
 ERTS_PATH="$MIM_DIR/erts-$ERTS_VSN/bin"
 ERL="$ERTS_PATH"/erl
 EPMD="$ERTS_PATH"/epmd
@@ -264,9 +265,13 @@ ctl ()
 
 ctlexec ()
 {
+    export EMU=beam
+    export BINDIR=$ERTS_PATH
+    export PROGNAME=erl
     CONN_NAME=$1; shift
     COMMAND=$@
-    "$ERL" \
+    $ERTS_PATH/erlexec \
+      -boot "$MIM_DIR/releases/$APP_VSN/start_clean" \
       $NAME_TYPE ${CONN_NAME} \
       -noinput \
       -hidden \