mavlink: Use polling fd, hack to prevent crash #2357

Job	Run time
variables	1s
fc_matrix (saluki-nxp93_default) / build	9m 9s
fc_matrix (saluki-pi_custom_keys, Tools/saluki-sec-scripts/custom_keys/saluki-pi/px4_bin_ed25519_... / build	10m 18s
fc_matrix (saluki-nxp93_flat) / build	6m 43s
fc_matrix (saluki-pi_amp) / build	10m 11s
fc_matrix (saluki-pi_default) / build	9m 23s
fc_matrix (saluki-pi_flat) / build	7m 12s
fc_matrix (saluki-v2_amp) / build	9m 17s
fc_matrix (saluki-v2_custom_keys, Tools/saluki-sec-scripts/custom_keys/saluki-v2/px4_bin_ed25519_... / build	9m 30s
fc_matrix (saluki-v2_default) / build	9m 25s
fc_matrix (saluki-v3_amp) / build	9m 34s
fc_matrix (saluki-v2_flat) / build	6m 55s
fc_matrix (saluki-v3_custom_keys, Tools/saluki-sec-scripts/custom_keys/saluki-v3/px4_bin_ed25519_... / build	9m 30s
fc_matrix (saluki-v3_default) / build	9m 41s
fc_matrix (saluki-v3_flat) / build	7m 6s
build px4fwupdater	1m 59s
upload builds to UAE artifactory	5m 4s
upload px4fwupdater to docker registry	2m 54s
upload px4fwupdater to UAE docker registry	0s
	2h 13m 52s

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