build-system: add travis_wait shell functions

These come originally from https://github.com/travis-ci/travis-build and are
available when running on Travis, but not when running inside a Docker
container on Travis as we do in order to build for Android.

The goal is to provide a quasi heart-beat on STDOUT during very long running
commands - without this the wget to download Qt often times out, so that's
where we are going to use this.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

scripts/travis-wait.sh

@@ -0,0 +1,65 @@
+#!/bin/bash
+# SPDX-License-Identifier: MIT
+# SPDX-Copyright: Copyright (c) 2016 Travis CI GmbH <contact@travis-ci.org>
+#
+# this is based on code from https://github.com/travis-ci/travis-build
+
+travis_wait() {
+  local timeout=$1
+
+  if [[ $timeout =~ ^[0-9]+$ ]]; then
+    # looks like an integer, so we assume it is a timeout
+    shift
+  else
+    # default value
+    timeout=20
+  fi
+
+  local cmd="$@"
+  local log_file=travis_wait_$$.log
+
+  $cmd &>$log_file &
+  local cmd_pid=$!
+
+  travis_jigger $! $timeout $cmd &
+  local jigger_pid=$!
+  local result
+
+  {
+    wait $cmd_pid 2>/dev/null
+    result=$?
+    ps -p$jigger_pid &>/dev/null && kill $jigger_pid
+  }
+
+  if [ $result -eq 0 ]; then
+    echo -e "\nThe command $cmd exited with $result."
+  else
+    echo -e "\nThe command $cmd exited with $result."
+  fi
+
+  echo -e "\nLog:\n"
+  cat $log_file
+
+  return $result
+}
+
+travis_jigger() {
+  # helper method for travis_wait()
+  local cmd_pid=$1
+  shift
+  local timeout=$1 # in minutes
+  shift
+  local count=0
+
+  # clear the line
+  echo -e "\n"
+
+  while [ $count -lt $timeout ]; do
+    count=$(($count + 1))
+    echo -ne "Still running ($count of $timeout): $@\r"
+    sleep 60
+  done
+
+  echo -e "\nTimeout (${timeout} minutes) reached. Terminating \"$@\"\n"
+  kill -9 $cmd_pid
+}