Pipeline improvements (#964)

* Fix bug with toll-gate validation against master
* Change cppcheck to not attempt to validate headers directly and
  to run on the entire codebase in the pipeline.
* Support running Arduino test and examples build in parallel

.ci/pipeline.groovy

@@ -121,6 +121,9 @@ def call(Closure body) {
 					stage('ArduinoMega (tests)') {
 						arduino.buildArduinoMega(config, config.tests, 'Tests')
 					}
+				}
+			}, ArduinoExampleBuilds: {
+				lock(quantity: 1, resource: 'arduinoExampleEnv') {
 					stage('MySensorsMicro (examples)') {
 						arduino.buildMySensorsMicro(config, config.examples, 'Examples')
 					}