Add GitHub Actions CI build (#11454)

This PR adds a CI build using GitHub Actions.
Besides having a backup for Jenkins, it will also make it easy for contributors to use a GitHub Actions build with their fork.

It features the following:

* Uncluttered simple build progress like we used with Travis CI
* Uploads the full build log and SAT summary report so they can be downloaded for further analysis
* Uses a Maven repository cache to speed up builds (first build takes a bit longer)
* Has some maven.wagon configuration options to prevent Maven Central artifact download issues from Azure
* Uses a matrix so we can easily add builds for other OS-es or newer Java LTS versions in the future

Signed-off-by: Wouter Born <github@maindrain.net>

.github/scripts/maven-build

@@ -0,0 +1,43 @@
+#!/bin/bash
+
+BUILD_LOG=build.log
+DEFAULT_ARGUMENTS="clean verify -B -T 1.5C -U"
+
+function print_reactor_summary() {
+    local start_end=$(grep -anE "\[INFO\] \\-{70,}" "$BUILD_LOG" | tail -n4 | cut -f1 -d: | sed -e 1b -e '$!d' | xargs)
+    local start=$(awk '{print $1}' <<< $start_end)
+    local end=$(awk '{print $2}' <<< $start_end)
+    cat "$BUILD_LOG" | sed -n "${start},${end}p" | sed 's/\[INFO\] //'
+}
+
+function mvnp() {
+    set -o pipefail # exit build with error when pipes fail
+    local reactor_size=$(find -name "pom.xml" | grep -vE '/src/|/target/' | wc -l)
+    local padding=$(bc -l <<< "scale=0;2*(l($reactor_size)/l(10)+1)")
+    local command=(mvn $@)
+    exec "${command[@]}" 2>&1 | # execute, redirect stderr to stdout
+        tee "$BUILD_LOG" | # write output to log
+        stdbuf -oL grep -aE '^\[INFO\] Building .+ \[.+\]$' | # filter progress
+        stdbuf -o0 sed -uE 's/^\[INFO\] Building (.*[^ ])[ ]+\[([0-9]+\/[0-9]+)\]$/\2| \1/' | # prefix project name with progress
+        stdbuf -o0 sed -e :a -e "s/^.\{1,${padding}\}|/ &/;ta" # right align progress with padding
+}
+
+mvn -v
+echo
+
+if [ $# -ge 1 ]; then
+    mvnp $@
+else
+    mvnp $DEFAULT_ARGUMENTS
+fi
+
+status=$?
+echo
+
+if [ $status -eq 0 ]; then
+    print_reactor_summary
+else
+    tail -n 2000 "$BUILD_LOG"
+fi
+
+exit $status