mavlink: Use polling fd, hack to prevent crash #2356

Job	Run time
variables	1s
fc_matrix (saluki-nxp93_default) / build	9m 24s
fc_matrix (saluki-pi_amp) / build	9m 39s
fc_matrix (saluki-nxp93_flat) / build	7m 1s
fc_matrix (saluki-pi_custom_keys, Tools/saluki-sec-scripts/custom_keys/saluki-pi/px4_bin_ed25519_... / build	9m 45s
fc_matrix (saluki-pi_default) / build	9m 35s
fc_matrix (saluki-v2_amp) / build	9m 18s
fc_matrix (saluki-pi_flat) / build	7m 36s
fc_matrix (saluki-v2_custom_keys, Tools/saluki-sec-scripts/custom_keys/saluki-v2/px4_bin_ed25519_... / build	13m 34s
fc_matrix (saluki-v2_default) / build	9m 40s
fc_matrix (saluki-v2_flat) / build	6m 57s
fc_matrix (saluki-v3_amp) / build	9m 31s
fc_matrix (saluki-v3_custom_keys, Tools/saluki-sec-scripts/custom_keys/saluki-v3/px4_bin_ed25519_... / build	9m 28s
fc_matrix (saluki-v3_default) / build	9m 48s
fc_matrix (saluki-v3_flat) / build	7m 14s
build px4fwupdater	2m 8s
upload builds to UAE artifactory	3m 45s
upload px4fwupdater to docker registry	4m 21s
upload px4fwupdater to UAE docker registry	0s
	2h 18m 45s

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