test: Add a semaphore shell test

This test tests new language features and as a fan in-out graph.

test/shell/sema-2.mcl

@@ -0,0 +1,15 @@
+# fan in-out
+exec ["exec1", "exec2", "exec3", "exec4", "exec5", "exec6", "exec7",] {
+	cmd => "sleep 10s",
+	shell => "",
+	timeout => 0,
+
+	Meta:sema => ["s:2",],
+}
+
+Exec["exec1"] -> Exec["exec4"]
+Exec["exec2"] -> Exec["exec4"]
+Exec["exec3"] -> Exec["exec4"]
+Exec["exec4"] -> Exec["exec5"]
+Exec["exec4"] -> Exec["exec6"]
+Exec["exec4"] -> Exec["exec7"]

test/shell/sema-2.sh

@@ -0,0 +1,8 @@
+#!/bin/bash -e
+
+# should take at least 55s, but fail if we block this
+# TODO: it would be nice to make sure this test doesn't exit too early!
+$timeout --kill-after=120s 110s "$MGMT" run --converged-timeout=5 --no-watch --no-pgp --tmp-prefix lang --lang sema-2.mcl &
+pid=$!
+wait $pid	# get exit status
+exit $?