Support --help in daml trigger/daml script/daml script-test (#4534)

fixes #4529
fixes #4530
fixes #4531

changelog_begin
changelog_end

daml-script/runner/src/main/scala/com/digitalasset/daml/lf/engine/script/RunnerConfig.scala

@@ -72,6 +72,8 @@ object RunnerConfig {
       }
       .text("Path to a file containing the input value for the script in JSON format.")
 
+    help("help").text("Print this usage text")
+
     checkConfig(c => {
       if (c.ledgerHost.isDefined != c.ledgerPort.isDefined) {
         failure("Must specify both --ledger-host and --ledger-port")

daml-script/runner/src/main/scala/com/digitalasset/daml/lf/engine/script/TestConfig.scala

@@ -53,6 +53,8 @@ object TestConfig {
       }
       .text("TTL in seconds used for commands emitted by the trigger. Defaults to 30s.")
 
+    help("help").text("Print this usage text")
+
     checkConfig(c => {
       if (c.ledgerHost.isDefined != c.ledgerPort.isDefined) {
         failure("Must specify both --ledger-host and --ledger-port")

dev-env/bin/daml-sdk-head

@@ -92,7 +92,7 @@ else
 fi
 
 cat > $DAML_HOME/bin/daml-head << EOF
-#!/bin/bash
+#!/bin/sh
 exec env DAML_SDK_VERSION=0.0.0 $DAML_HEAD_SDK/daml/daml "\$@"
 EOF
 chmod +x $DAML_HOME/bin/daml-head

triggers/runner/src/main/scala/com/digitalasset/daml/lf/engine/trigger/RunnerConfig.scala

@@ -70,6 +70,8 @@ object RunnerConfig {
       }
       .text("File from which the access token will be read, required to interact with an authenticated ledger")
 
+    help("help").text("Print this usage text")
+
     cmd("list")
       .action((_, c) => c.copy(listTriggers = true))
       .text("List the triggers in the DAR.")