build: enable `failOnWarning` #1757

Job	Run time
build_timeline	2m 45s
download_test_data (physics)	3s
download_test_data (detectors)	3s
test_swifjob (physics)	2m 15s
run_histogram (physics)	2m 48s
run_histogram (detectors)	2m 53s
test_swifjob (detectors)	1m 51s
run_analysis (physics)	2m 30s
run_analysis (detectors)	5m 55s
	21m 3s

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