[jnigen] Fix summarizer and improve errors #157

Job	Run time
build_jni_example_windows	2m 59s
analyze_jnigen (stable)	39s
analyze_jni	1m 2s
build_jni_example_linux	1m 12s
run_pdfbox_example_linux	2m 26s
build_jni_example_android	3m 13s
test_jnigen_windows_minimal	6m 19s
test_jnigen_macos_minimal	2m 56s
test_jnigen (ubuntu-latest, stable)	7m 59s
test_jnigen (ubuntu-latest, beta)	7m 56s
test_jni_macos_minimal	1m 23s
test_jni	1m 41s
test_jni_windows_minimal	4m 56s
coveralls_finish	2s
	44m 43s

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