Add missing rc.sysinit file in the ROMFS #288

Job	Run time
build (check_format)	57s
build (check_newlines)	1m 26s
build (tests)	5m 36s
build (tests_coverage)	7m 24s
build (px4_fmu-v2_default stack_check)	3m 15s
build (validate_module_configs)	54s
build (shellcheck_all)	1m 36s
build (NO_NINJA_BUILD=1 px4_fmu-v5_default)	4m 3s
build (NO_NINJA_BUILD=1 px4_sitl_default)	3m 18s
build (px4_sitl_allyes)	4m 19s
build (airframe_metadata)	59s
build (module_documentation)	1m 10s
build (parameters_metadata)	1m 5s
	36m 2s

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